I'm getting the same error. In my case, I am connecting to Dynamics 365 Business Central. I'm doing this from a "Canvas". I am able to connect, and choose a table for my app. I am then allowing PowerApps to populate the form with my fields. I then save the app, and run it. When I do this, it simply hangs.
I've tried to do a "Crtl-Righ Click", but this doesn't retrieve a session ID (or anything else). I find it strange that I can connect and select a table, but get no data when I try run the app.
BTW, I created two apps yesterday that both access online Business Central. Both apps give me the "getting your data..." message. I allowed one to stay open on my screen for about 1/2 hour just to be sure it was truly hanging.
Have you taken a try to run your app within Preview Mode? Does this issue also occur?
Which browser do you use to run your published app?
I have made a test on my side, and don't have the issue that you mentioned. Please take a try to run your app within Preview Mode, then check if the issue still exists.
Please consider take a try to turn off/disable the "Improved app rendering (final validation)" option and "Delayed load" option within Advanced settings of App settings, then re-publish your app, run your app again to check if the issue is solved.
In addition, please consider take a try to clear cache of your browser, then run your app again, check if the issue still exists.
If the issue still exsits, please consider submit an assisted support ticket through the following link: