Azure form recognizer app invalid resource name
I had the same error. It turned out to be due to incorrect SAS URI formatting because I generated and copied the SAS token via the Storage Accounts interface. It's much easier to get the correct format for the SAS URI if you generate it through the Storage Explorer (currently in Preview) as opposed to through the Storage Accounts.
If you read the documentation carefully it gives you a step by step guide
"To retrieve the SAS URL, open the Microsoft Azure Storage Explorer, right-click your container, and select Get shared access signature. Set the expiry time to some time after you'll have used the service. Make sure the Read, Write, Delete, and List permissions are checked, and click Create. Then copy the value in the URL section. It should have the form: https://.blob.core.windows.net/?"
The error messages point to a configuration issue with the AzureBlobStorageTemplate Thing. Most likely the containerName field for the Blob Storage Thing is empty or contains invalid characters
Ensure the containerName is a valid Azure storage container name.
Check https://docs.microsoft.com/en-us/rest/api/storageservices/Naming-and-Referencing-Containers--Blobs--and-Metadata for more information.
A container name must be a valid DNS name
The Connector loads and caches all configuration settings during startup. Any changes that you make to the configuration when troubleshooting are ignored until the Connector is restarted.
When creating the container connection, you must add the container into the SAS URI, such as
https://<storage-account>.blob.core.windows.net/<Enter-My-Container-Here>?<SAS Key>