Thanks for reaching out to us, this may be caused by incorrect CORS setting. I have posted the same solution in below thread as well:
https://learn.microsoft.com/en-us/answers/questions/587119/form-recognizer-studio-custom-form-stucks-at-34loa.html
The workaround works for me is:
Add a new rule for my storage account .
Configure cross-domain resource sharing (CORS) on the Azure Storage blob Enable CORS on your storage account. Select your storage account in the Azure portal and then choose the CORS tab on the left pane. On the bottom line, fill in the following values. Select Save at the top.
Allowed origins =
Allowed methods = [select all]
Allowed headers =
Exposed headers = *
Max age = 200 (here I am using 1800, but 200 should be enough)
Then everything works fine for me. Besides that, please make sure your storage account is under Standard performance and your container is Public access level to Container (anonymous read access for containers and blobs).
Hope this will help. Please let us know if any further queries.
Regards,
Yutong
-Please kindly accept the answer if you feel helpful, thanks!