Telling us which app might help? If you've blocked any app permissions or anything like that it would also help to know. Also has the app never worked on this phone, or did it stop working? If the latter, were there any changes at that time (app update, system update, change of ROM, etc)?
Edit: that was written before the thread merge, so now we know what app. However it would still be useful to know whether you have done anything else, such as refusing permissions or firewalling, which might affect the function of the app in any way.
In the absence of other information, generic solutions would be to wipe the app's cache (which is different from the system cache) or uninstall and reinstall the app (edit: if you've tried an older version we can consider this test done). If none of that works you could try contacting the app developer to let them know - it might be that the app is not compatible with your phone and its current software version, but the developer may not know that if nobody has told them.