Can't connect to Plex Server. Wifi blocks it

Hi

Ive been looking almost everywhere for the last couple of days, for a solution to my problem. Im trying to fix my sisters connection to our plex server, but its like the wifi blocks the connection. She can connect via 3g/4g internet on her phone so i know its because of the wifi.

Im not the most amazing wifi configurator so hopefully one of you guys can help me figure this out.

She only has one router/modem in the house.

Removing firewall didnt work

I changed DNS to google’s, 8.8.8.8, didnt work

I have a configuration that says “router mode” on/off, on wifi, but she only has one router.

I tried “specify manual port 32400” on plex settings, but it wont allow me to connect.

Please help! Thank you very much

Is the Plex server not located in your sisters house?

No, its not

have you tried telnet your Plex server from your sister’s house. How are you trying to connect, using Plex Player or directly ?

What kind of wifi is this like what vendor?
And when on wifi not 3/4g can you get to plex.tv/web from her phone?