updated with info about PVID

TL-SG3424.md

@@ -134,9 +134,13 @@ To change to TRUNK, select the ports on the left that you want to change, then c
 
 Do not try to change the PVID here. It will fail (inexplicably).
 
-## Managing LAG and LACP Configurations
+### Troubleshooting
+
+If you get errors about the PVID when changing VLANs accessible on a TRUNK port, change it to a VLAN that will be on the TRUNK after the changes.
 
+## Managing LAG and LACP Configurations
 
+**TODO**
 
 ## Managing STP configurations