When it's running a stock rom, all I have to do to get onto T-Mobile is go under network settings and select 'GSM/UMTS', and bam I'm connected getting great speeds. With every 4.4 rom I've tried, there are WAY more options under network settings including probably 8 options that contain GSM in one way or another, but after going through every option on the list and then turning airplane mode on/off, not a single one gives me any signal whatsoever, let alone a data connection.
There are a couple GSM options that let me search for network providers, and it finds T-Mobile and AT&T, but then selecting T-Mobile just hangs on a screen that says 'registering with T-Mobile' (what??) and eventually that times out and I still have no connection.
Sorry if this is a simple or common issue, but I haven't seen anyone else mention this on the newer roms so I'm worried it's just me.