Hello,
Unfortunately you're not the only one experiencing this bug:
https://forums.autodesk.com/t5/civil-3d-forum/viewport-is-view-locked-switching-to-paper-space/td-p/...
They haven't formulated a solution yet, but I would start with the following heuristic to try and solve the issue:
Is it only in one drawing or in all your drawings?
- If only in one drawing, perform an audit on the drawing and a -purge/regapps (share the problem drawing here)
-- If the problem persists, try to delete the layout and recreate the layout
-- If the problem persists, use WBLOCK to save your model space to another .dwg then recreate the layout/viewport.
- If it is in all your drawings, check to see if the problem also happens for other people/installations
-- If the problem happens only for you, try resetting your AutoCAD profile and try again
-- If the problem persists, try resetting your AutoCAD to default settings and try again
-- If the problem persists, try a clean uninstall and re-install of AutoCAD
-- If the problem persists, try it with a different windows user. If that fixes the issue, you might need to redefine your windows profile.
- If the problem happens for all your colleagues, then see what happens if you store the drawing in a different location, or if you open it from another network.
Contact Autodesk support directly https://www.autodesk.com/support/contact-support to have them help troubleshoot the issue.
