We are in the middle of a migration and moving from SQL 2012 Enterprise to SQL 2019 Standard (due to licensing costs) and I have recently encountered this issue using sp_blitz.
With the results looking like this , notice offline schedulers. I have been working with my VM team to reconfigure but not sure they or I 100% understand this correctly to resolve.
with select * from sys.dm_os_schedulers showing this
I am not familiar with the VM configuration to know exactly what to tell them. I think this change has improved (somewhat) but it still doesnt seem like SQL is taking advantage of everything on the VM.
Users have been complaining of performance on the migrated applications and I think this is the issue as the underlying hardware is much more powerful than the old 2012 VM's.