Symptoms

ABBYY FineReader Server 14 can not process any files when SharePoint is used and throws the following error in the Event logs:
"ABBYY FineReader Server Workflow "<WorkflowName>": An error occurred while processing the file '<FileName>': Cannot send a content-body with this verb-type."

Cause

ABBYY FineReader Server 14 stops working because of the large database size which is caused by a lot of pending/failed tasks in the database. 
Failed/pending tasks might be caused by the SharePoint authorization problem

Resolution

Microsoft OAuth Authentication method should be used.
Navigate to Workflow properties --> Input --> Select Library... --> Credentials... --> Use Microsoft OAuth --> Sign in...

Additionally, if a basic authentication is used or the issue is not resolved by reconfiguring to OAuth, there is a recommendation for updating to the latest build of FineReader Server 14, as the following behavior is a bug and has been fixed in the FineReader Server 14 R3 Update 8.1 (14.0.3.427)

Note: The latest build of ABBYY FineReader Server 14 can be downloaded via the link:

FineReader Server Latest release