(See update below)
Just had the situation(V2025 onwards) that drawing views where not able to be Regened. Or that Regen option was turned off for that sheet.
RMB on Selected View/Attributes to see if the Regen is active or greyed out.
But why was this occurring?
From v2025, some new capability in the 2D Sheet Configuration are active by default, that perhaps unintentionally, turn off View Regen.
It appears to be be that the Configuration active during the sheet creation, embeds a flag in the sheet turning off Regen. You can see the Regen Attribute shaded out during View insertion.
The fix requires the turning of of the Discrete Projection option AND creating a new drawing sheet.to replace the old one.
Adding new sheets to the original drawing does not solve the problem.
Text and other added markup can be copied from the original sheet to the new no problem.
To check, Utilities/Configuration/2D - Drawing Sheet…
UPDATE:
Discrete projection is a new drawing creation mode that is faster than the older method.
By default it ALWAYS regenerates. This means you cannot turn the view Regen OFF, hence the Regen Control option is greyed out. It is perhaps a little confusing as we are used to seeing the active regen highlighted. IMO, it might have been better to lock the option in the highlighted mode.
If you want to create a drawing view that is not intended to regen, you must change the projection method before creating the drawing.
The requirement to Stop a view regen is rare. If you are one of those who uses it to show stages of a part construction, then the RMB/History/State option is a much better solution.
Config setting location.
Cheers - Paul