rowina
There is no problem with the app or the settings, you just need to make adjustments...
You may do this :
On the first page there is a list of real proxy servers. mixmatch them with your proxy server until you get a good connection. there will be a right combination for your location. patience is required.
Sometimes your area have trees covering your spot making the signal of your sim network weak. The same goes with buildings that have areas where no signal can penetrate.
or...
maybe your phone is not compatible to the vpn app.
Why don't you try TNT ma'am.