Recreational / Hobbyist UAS pilot reported unintentionally flying over a restricted area. Pilot stated the airspace app they normally used was retired and they did not use any of the other available apps.

Narrative

How the problem arose:I was controlling the drone from the roof balcony of an apartment building I'm staying in to ensure line-of-sight contact during the operation. It had been a while since I had flow a drone in congested airspace; so I opened the B4UFly app to check airspace and restrictions. The app said the service is no longer available; and when I clicked on the link to the FAA website; my phone's browser gave me a 404 Error. I closed the app and tried again; and it gave me the same issue. Instead; I looked closely at the ZZZ TAC (Terminal Area Chart) at the area to verify there were no Special Use Airspace; Restricted Airspace; and Airport proximity. I determined the drone would be in Class G airspace the entire flight; and there were no NOTAMs; TFRs; or restricted airspace in the zone at the time. I knew Location X was across the water; and my intention was the remain away and clear of the area to respect its security. During the flight; I was pointing the drone's camera to the northwest while maneuvering near the end of the channel as the drone was slowly moving backward (I was using the reverse camera to monitor obstacles or conflicts). During this maneuver; a prompt came up on the screen of the controller about entering an Enhanced Warning Zone. I discontinued the maneuver; acknowledged the prompt and was a bit puzzled; because I didn't see anything prior to the flight that would warrant that within the ZZZ TAC; TFRs; or NOTAMs. I returned the drone to over the open water; and continued the flight to completion.How it was discovered:The particular flight in-question ended uneventfully. Later in the everything (same day); I prepared to launch the drone again to get some shots of the city lights coming alive at dusk. As I was wrapping up the flight and returning the drone to the landing zone; 3 Law Enforcement Officers approached me on the balcony and asked for me to return the drone. Of course; I happily complied. Once the drone was secure and shut down; I had a respectful dialogue with the officers about a raised concern from local authorities of a drone flying over the restricted area. Upon inspecting the officer's screenshot of the flight track; and comparing it to my own; it did appear that I overflew an Enhanced Warning Zone covering the restricted area; as well as a correctional facility (which is right next to it). It's a small warning zone at the end of the channel that I overflew while getting a wide-angle shot of the city pointing northwest (the restricted area was underneath the drone; and I didn't see it or know about the warning zone). The officers did not issue a citation; as we had a respectful and informative dialogue to debrief what happened.Contributing Factors:The B4UFly App being decommissioned interrupted what would be my normal pre-flight planning; and I resorted to an alternate method of airspace/NOTAM/TFR verification; which proved to be insufficient in the case of the restricted area (it's not marked on the ZZZ TAC in any regard). Additionally; the fact that the drone's main camera was pointed northwest while it was backing up and panning inhibited my view of the land boundaries below me (I was using the 360º 'backup' camera during the maneuver to ensure obstacle clearance; but wasn't immediately thinking about the land boundary). The third contributing factor involved my lack of situational awareness of the Enhanced Warning Zone over the restricted area. During the maneuver; the drone prompted me about the drone entering an Enhanced Warning Zone; which led me to discontinue the maneuver and acknowledge the prompt. This confused me; as I wasn't aware of the area; but I left that area and continued the flight until landing.Corrective Actions:Now; on a computer browser; I've navigated to the FAA page which B4UFly was trying to link to; and I'm now aware of the apps that have replaced B4UFly as of February 2024. I've setup the LAANC app; AirHub Portal; and my corrective actions are asfollows: 1) I've committed to not allow myself to launch a drone until I have opened the app and checked all surrounding restrictions and notices. If an error occurs; I will turn to another FAA-Approved LAANC app before launching. 2) I'll cross-check these maps with the applicable VFR chart; FAA TFRs; NOTAMs; and traffic for the area. 3) Query the FlySafe Database on-board the drone before each flight to ensure it has the most up-to-date Geo-Zone maps installed.That being said; I feel it is rather confusing for drone operators that DJI's Geo-Zones which govern where it can/cannot fly (it will physically stop the drone if it approaches a no-fly zone) don't align with the restrictions that are outlined on FAA LAANC maps. I was under the impression that an 'Enhanced Warning Zone' was a 'fly with caution' area; and not an outright prohibition. Upon further research; it seems other drone operators have had the same confusion. The proper corrective action; on my part; is to employ an FAA-Approved LAANC app on a consistent basis; and to remember that checking a VFR chart; NOTAMs; TFRs; and monitoring manned traffic ALONE is not sufficient.Conclusion:As I told the Police Officers; I'm grateful for any opportunity to learn from my mistakes; and the pleasant interaction with authorities about the security concern proved to be an educational experience that has undoubtedly increased my awareness.