So I invested in VPN a while ago, and everthing has been fine, except recently. For some reason, OpenVPN refuses to connect over my cellular data connection.
It works perfectly on WiFi and I can’t figure out what the problem is.
The notification is stuck on “Waiting for server reply.”
The last line in the log appears to be:
2017-06-04 13:49:30 MANAGEMENT: >STATE:1496598570,WAIT,,,,,,
I had this problem with PiA last year. I was able to use it on WiFi but not on mobile data. I think I overcame this problem with changing Udp to Tcp or sth like that, or by changing port number , I cannot remember. 
I would recommend to try another VPN and see if it’s a problem with the provider or your phone. You could try a trial account with IVPN, Mullvad, OVPN, AzireVPN…
Your ISP could be blocking the port your vpn provider picks up, some vpn providers use randomized port number to connect, it could be restricted, play with ports and see.
What version of Android? 4.4.x has issues with VPNs over cellular.
Changing to TCP didn’t help.
Are there any ports in particular that I should try?
And should they be UDP, TCP, or both?
6.0
It was working, then suddenly stopped.
Try port 443, 8080, 80 or 53 (53 is DNS port so it is unlikely to be blocked, can be a slight bit slower however).
I suggest UDP, but sometimes UDP does not work in that case, do TCP.
Does the app provide any logging of each connection attempts or connections? It could have the solution in there.
Do they provide PPTP/L2TP to see if its something with app itself to do or for certain with your mobile ISP to do.
Edit: Ticking “both” makes the app decide what to decide, try UDP if that does not work, pick TCP.
Don’t let app to search for random ports, it will work less likely, so if possible, close all “auto” settings and make it manual.
Tried all of the combinations of ports and protocols, , but none connected. Not even on WiFi.
Which is weird, my VPN should support TCP on port 443, but it won’t connect.
They also only support OpenVPN.
Contact VPN provider and ask for a solution, if none then get refund as the VPN does not work as it should for your device.
I hope their sales are not final (don’t know which VPN service it is).
Well, maybe it’s better to use another service if it doesn’t work?