This has been an issue on and off over the last couple of days for me as well. Unable to play my App for the last 4 hours. It appears to have happened with the recent version change to 3.19081.20. It worked on 3.19075.25 (4 hours ago) but the issue I am having now also happened on 3.19075.21.
I have noticed also that it is taking between 10-15 minutes to load the App in studio for editing (queue elevator music...)
Offering up this information to help resolve what appears to be a wider issue (but would really appreciate it being solved for me too).
Most recent Session ID is 935d3562-7d85-42b7-95ad-64e51d59ca48 (version 3.19081.20)
I have escalated with a support ticket. The App will not play (and hasn't) for the last 3 days now.
I suspect a rogue component or control somewhere that is preventing the App from compiling when it is being published. Other Apps are working - just this one isn't playing and taking a long to load for editing.
PS - I am not using any cascading dropdowns and running Azure SQL.
The cascading works fine within PowerApps, however, the values are not being saved in the SharePoint list. This started happening this week. I havent touched the app in over 5 months. Im using LogicApps to create the item and send the email for approvals. All fields are saving in the List except for the Cascading fields.