I don't know what's wrong then.
You could take my ROM zip from my signature, delete all the partition IMG files out of it, put the modem.img you want in, and edit the updater-script to remove anything having to do with flashing the other partitions, then flash the resulting zip in TWRP. Make sure you know how to recover and have everything saved that you want to keep from internal storage in case you do something wrong, though.
---------- Post added at 08:06 AM ---------- Previous post was at 08:04 AM ----------
You know, I haven't been able to get mobile data working on any CM-based ROM on the VK810 yet, so that's probably your trouble. If you want mobile data you'll have to go stock. Some people had some luck on CM-based ROMs but then eventually it stopped working. I didn't have any luck at all.