WireGuard tunnels not connecting over mobile cellular network Host and Client doesn't receive anything

[null-p01ntr]

I extensively use my mobile phone connected to my home network on the go and as a hotspot for my laptop. Recently I was unable to connect to my VPN through any of my configurations when I use my phone network. I tried with a different sim card too (same carrier) no luck. How should I trace my problem? Is there a known workaround to this?
I find "only connecting with mobile and no connection on wifi" but I'm having the opposite one. I can connect over public and private networks but not with my own mobile network.

More details about my problem (debug output etc.): https://github.com/pivpn/pivpn/issues/1821
(I live in Turkey, using Vodafone)

[orazioedoardo]

only connecting with mobile and no connection on wifi

You CAN use wifi or whatever connection you want, FAQ however advised to use different network to test rather than the same network where PiVPN is located.

I can connect over public and private networks but not with my own mobile network.

Try this https://docs.pivpn.io/faq/#tweaking-mtu

[null-p01ntr]

I don't have a problem using wifi connections (ex: friends and cafe wifis not my home wifi with pivpn)

I found out my local advised MTUs are 1458, 1492, 1467, 1450, 1430. I change on the mobile app directly and unfortunately none of them worked.

How can I find the absolute right value and how can I trace if I'm in the right direction while incrementing and decrementing MTU?
I always get a handshake fail after 5 seconds. No packets on anyside I am not experienced in these kinds of networking adjustments.

I tried my sim on different devices too, no luck.

I had the same setup working without MTU tweak for months without any issue.

[null-p01ntr]

Can this issue be about port forwarding?

This is my current settings on modem interface. (Always been like this)
192.168.1.13 is the raspberrypi's IP

[orazioedoardo]

Can you confirm you can connect from networks other than your cellular network?

[null-p01ntr]

I checked with other carriers and wifi networks. I can confirm that connection is successful on Wi-Fi networks and failed on mobile networks. (whether using on mobile or with hotspot)

I also tried changing my APN between v4, v6 and v4/v6 but no luck.

[orazioedoardo]

If it works on some network and not on others even after reducing the MTU i'd say those networks may be blocking wireguard.

[null-p01ntr]

It seems like it was my carrier blocking the WireGuard protocol.
I found an expert on the topic who had the same issue as me with the same carrier. He had a solution by bypassing the protocol censoring.
His instructions: https://keremerkan.net/posts/udp2raw-bypass-censoring-wireguard-protocol/.
I didn't try it yet because it doesn't fit my use case, I will try OpenVPN for now and see how it goes