VTP - Client can't modify VLANs
When configuring VTP, a switch that is configured as a client cannot make any changes to VLANs. This is the case for all versions of VTP.
If an attempt is made to make such a change, the following error message appears:
%VTP VLAN configuration not allowed when device is in CLIENT mode.
Only VTP servers can make changes. In the case of VTPv3, only primary servers can make such changes.
Links:
https://forum.networklessons.com/t/introduction-to-vtp-vlan-trunking-protocol/870/191?u=lagapidis
https://networklessons.com/switching/introduction-to-vtp-vlan-trunking-protocol