I have found a possible cause of the issue:
I use the "partedUtil get" command to get the information of the disk and it prints the following
Error: The backup GPT table is not at the end of the disk, as it should be. This might mean that another operating system believes the disk is smaller. Fix, by moving the backup to the end (and removing the old backup)? This will also fix the last usable sector as per the new size. diskSize (5857345536) AlternateLBA (3904897023) LastUsableLBA (3904896990)
Warning: Not all of the space available to /dev/disks/naa.6d4ae520b08d0d001810d3ca2cb37f6e appears to be used, you can fix the GPT to use all of the space (an extra 1952448512 blocks) or continue with the current setting? This will also move the backup table at the end if is is not at the end already. diskSize (5857345536) AlternateLBA (3904897023) LastUsableLBA (3904896990) NewLastUsableLBA (5857345502)
364602 255 63 5857345536
1 2048 3904896990 0 0
So it might be the wrong location of the backup GPT table causes the vShpere to disable the increase button in the UI (disk not recognized properly)?
Does it make sense?
PS: I cannot not fix the GPT table right now because of other concerns.
Thank you,
KuoHsin