After enabling vSAN File Service the network port group can't be changed.
VMware vSAN (All Versions)
vSAN File Services is enabled
vSAN File Service doesn't support file service network reconfiguration directly.
If the vSAN File Service network port group needs to be changed follow the steps below per the version in use.
For vSAN 7.x perform the following steps.
For vSAN 8.x and higher step 4 is not required as you can change the port group during re-enabling vSAN File Service.