Hi @jnhrv,
Thank you for posting in this community.
Based on your error message, it appears that the AgentManager connection failed.
Firstly, I would suggest that you check that the machine with SP migration agents installed has a good network link and is able to access the fileshare folder. And make sure that firewalls etc. are not blocking these accesses.
Secondly, If the password of the logged-in Tenant Administrator account has changed, or any other similar, critical changes applied to the Tenant Admin account that would require re-sign in, all of the agents will be disconnected and reinstallation is required on all of them.
Third, make sure the names of the files you scan are valid. See Invalid file names and file types in OneDrive and SharePoint.
Third, make sure that the path to the files you are scanning is not too long. See Invalid file names and file types in OneDrive and SharePoint. The entire path, including the file name, must contain fewer than 400 characters for OneDrive and SharePoint.Finally, if the problem still persists, I recommend checking out this official troubleshooting document about SP migration agents. You can look up the relevant error codes or download the Task Error Report to locate the more precise source of the problem.
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