Need help to (re)activate the native Android encryption

Dear all,
I need some help in (re)activating the native encryption in an Android 4.4.2 ROM.
The phone is a THL T6 PRO an was delivered with a Android 4.4.2 Stock ROM.
The normally available native encryption is not available in this ROM.
It is absolutely not visible (not only greyed out).
I am using a Custom ROM which is based on this Stock ROM and therefore the encryption is also not available.

I read dozens of threads, but nothing really helped me to find out, where the encryption is disabled or how to fix it.

The only interesting things concerning this topics which i found are:
- Android fstab file
- Partition layout, I ran the two patches without success.
CS_usrdata_fix-fs.zip
ICS_usrdata_shrink.zip
forum.xda-developers.com/showthread.php?t=2122702

I would be very glad, if someone could help to get the encryption working, which is really important for me.
I am really satisfied with everything else from the cutom ROM, which is:
http://klausminator.de/custom-rom-fu...nkmdroid-v0-8/
pw for download can be found on the website

Thanks a million, best regards

Harald