Based on your YEARS AGO i expect you are using old SDK Requirements, not using TargetSDK 26, not using rumtime permission, not using fileprovider.
Your app needs to get updated with the new requirements. It is of no help if one of us try to recompile your old source. Probably it is not working without rewriting parts of the app.
Update your B4A Version to be the newest Release (9) and do the changes by yourself after you got familar with them:
android.jar / targetSdkVersion / minSdkVersion
Also setup a new SDK.
You can find the Setup-Instructions here.
https://www.b4x.com/b4a.html
You also can watch this Video as it describes it clearly.
Start with a new Blank folder like you see in the Video.