I see this problem when I have sp_configure set to enable the 'set working set size' option. I get the same grayed-out symptom as you saw.

Example to repro:

sp_configure 'set working set size', 100

reconfigure

I believe that the root cause is that in SQL 2005 and above, the 'set working set size' option is not shown in Management Studio for the memory settings page, because it is out of favor as a memory setting, and is not functional in later version of SQL Server. Docs to suggest that are here https://msdn.microsoft.com/en-us/library/ms189056.aspx

When that setting is non-zero, I believe Management Studio grays out the dynamic memory settings (min server memory, max server memory) since the legacy working set options conflicts.

1. Check your current value like this in a query windows in SSMS:

sp_configure 'show advanced', 1

reconfigure

go

sp_configure 'set working set size'

go

Do you see the config_value is non-zero for that setting? (some positive number)

2. If so, (assuming you do not the really old SQL 2000 setting anyway), the workaround is to revert the set working set size back to the default zero.

sp_configure 'show advanced', 1

reconfigure

go

sp_configure 'set working set size', 0

reconfigure

go

sp_configure 'show advanced', 0

reconfigure

Thanks, Jason