Message: Error 1606. Could not access network location Revit 2021\.

After installing update Revit 21.1.10.26 (21.1.1 Hotfix)

https://knowledge.autodesk.com/support/revit-products/learn-explore/caas/CloudHelp/cloudhelp/2021/ENU/RevitReleaseNotes/files/2021updates/RevitReleaseNotes-2021updates-2021-1-1-html-html.html)

We have seen that the registry sometimes get a corrupt value on the Install location.

Check the HKLM registry under the SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\{7346B4A0-2100-0510-0000-705C0D862004} key and the "InstallLocation" value.

It should say something like "C:\ProgramFiles\Autodesk\Revit2021\". If it only says "Revit 2021\", it means that the Autodesk's upgrade has not been done correct.