getting error when switching project from standard to flex

[frindly]

My application deploys and runs fine when set as a standard, however when i switch the configuration to flex, it's failing after the application installs. The error isn't giving me any details as to what is going wrong and I can't find any other logs in my cloud console that may provide insights.

Finished Step #1
PUSH
DONE
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Updating service [gmail-sync] (this may take several minutes)...failed.                                        
ERROR: (gcloud.app.deploy) Error Response: [13] An internal error occurred.