Unable to connect with 5g network

Some of the users in my organisation are not able to access configured websites specified under the pritunl org. with 5g. For some of them are working.
I have already updated the pritunl to latest stable version and also the server supports MTU upto 1400 bytes.
What can I check further in order to mitigate the issue?

If the server only has a 1400 MTU you will need a lower MTU for the VPN connection. The VPN connection will also have overhead. Start at 1000 to verify if it is the MTU. The client debugging documentation has information on debugging the MTU.