HI,
Please do the following so you can get a more detailed answer that will help you/us get you working
1) Go to the main Make.powerapps.com page
2) click on Apps on the left side
3) Find your app in the My Apps, Shared with Me or All
4) Click the ... at the end of the line of your app name
5) Select details => Monitor
Let Monitor start up in your browser
6) On the monitor Tab, click the Play Published App
This will launch another tab that is now being debugged and captured by Monitor
7) Cause your Error to happen
8) Switch back to Monitor
9) In the Filter (top right) select Error
Now, usually an Error will cause more than 1 line in the output. You want to find the output that has 4 Tabs in the right side window
This should give you, on the 4rth Tab, the Response. In the Response tab, open the Header and Body (they are closed by default)
It should have, in either the header, or the body, a specific error that will show the Field, Permission etc that is the issue. Now you have the ability to fix that.