Why can I connect to vpn via mobile internet, but not via wi-fi?

Question

linux

I set up vpn on vds (via pptp protocol), but I ran into the following problem: I can connect to vpn only when I use mobile Internet. If I try to log in by connecting to wi-fi, then the following appears in the server logs:

Plugin /usr/lib/pptpd/pptpd-logwtmp.so loaded.
Using interface ppp0
Connect: ppp0 <--> /dev/pts/0
Hangup (SIGHUP)
Modem hangup
Connection terminated

As I understand it, the connection is closed by the client, not the server.

Answer 1

Well, ppp0 is not Wi-Fi
eth0, etc.

Answer 2

On the router, it is possible that Nat ppp needs to be activated and you can make your mtu smaller