So here's what happened to me (short version),

I used to be active in a band, or rather several bands, and I used to contribute to songwriting, everything from the occasional riff to everything for said project. Then I moved away, and far away from every musician I know and I just didn't write for awhile.

Now I am getting back into it, or trying anyway. I used to be able to churn out all kinds of music. Different genres, complex, simple, whatever. But these last few months I have just had loads of trouble and the occasional good part is all I've got, but that's not going to be enough. The reminder of what I used to do gives me a bit of hope, but overall trying diligently for little bounty is very discouraging.

What do you guys think happened to me and how do you all think I could overcome it?
Songwriting is a skill just like anything else, if you don't practice you'll lose your touch. All you can really do is buckle down and dig yourself out of this little rut of yours. Keep writing, and eventually it'll come back. Maybe revisit and even rewrite old pieces if possible, that's helped me once or twice when in similar situations.