Please check the CDS connection, is it connecting properly? Please just try to update the connection to see if it will work.
Do all the apps that were created based on CDS entities have the same issue?
Could you try to create a new app that relies on CDS entity to see if you will still get the issue?
Besides, apps that are based on CDS entities could be opened without issue on my side.
I tried to remove and CDS Entity and when trying to RE-ADD the DataSource, this is the error (I cannot add the CDS Entity BACK now 😞 😞 😞 (Panic):
I also tried creating a new app using CDS connection , but upon choosing the Datasource for the CDS it has the same error (see short clip)
"message": "The response is not in a JSON format.",
Session ID: 05cf4a41-a18d-4215-a3b6-ef30d0cf3751
@v-yamao-msft have done all your suggestions but still the apps are having the same error. I have already raised a ticket with Microsoft (1 week ago) and to-date , it is still unresolved.
[REG:118120519418181] PowerApps Pro Limited - All PowerApps using the CDS connection has stopped working , Error "Specified record was not found" at the homepage of each app Initial Response
PowerApps is now so unreliable, all our production apps using CDS have not been in use for almost 2 weeks now.
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