Hi @Happy1 ,
After my testing, no matter if I log in to the On-premises data gateway with an M65 account with any account, I can log in successfully.
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Since we can't reproduce your situation, we need to narrow down the problem and try some things.
1.Whether you downloaded the latest version of On-premises data gateway, try uninstalling and reinstalling the latest version to see if the problem disappears.
2.Check whether the network is normal?
3.Whether you can open the M356 sharepoint website?
4.Try to change a machine to see if the problem can be reproduced.
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