Inability to upload any files or externalize any content into and out of any particular site collection where externalization has been enabled.
Externalization attempts will generate this error:
Uploading any type of file to the site collection generates this error:
The BlobStoreAbstractClassVersion value is located on all WFE and APP servers in the machine.config file, which can be found here:
Here is how the value looks in the machine.config file:
<add key="BlobStoreAbstractClassVersion" value="10.50.0.0" />
After changing the BlobStoreAbstractClassVersion value from 22.214.171.124 to 10.50.0.0, on all SharePoint servers except for search and distribution cache servers, the ability to upload files into the site collection that had externalization enabled was restored and externalization from the site collection was also restored.
BlobStoreAbstractClassVersion in machine.config should be 10.50.0.0 for STP version 126.96.36.199
BlobStoreAbstractClassVersion in machine.config should be 188.8.131.52 for STP version 184.108.40.2060