SDcard not visible under android 5.1

Hello,
i bought a teclast X98 pro... But i think this issue could be the same on X98.

Under windows my SDcards are all fine...
In Android 5.1 i cant see my ext sdcard. I tried different SDcard sizes and partition formats ( fat, exfat)
i cant get it run... In the settings i see one SD card (disabled, means grey options)
Four USB-storages (disabled, means grey options)
I think this could be normal for all the windows partitions right ?
But how can i get my external SDcard to run ? For now i use Sandisk Ultra 16gb. Work fine in different phones and tablets and on the tablet i Windows 10.
I resetet the tablet to factory ... it didnt helped... But at the first startup i saw a message that the sd card was propably ejected out from the device... I didnt touch the device at startup...
Like i said before, in windows all works fine with a Sandisk 128 gb without problems...
I searched but didnt found anything...

Maybe anyone can help me with a good advice ?

thanks a lot for any help.
Cargoman

swap internal memory with sdcard or something on cm 12.1?

Im on D620 with last stable build of cm21.1 by nikita!
is there any solution for internal memory? or by any change your app data like whatsapp, fb, soundcloud can b placed on sd?
looking forward to suggestions, thankyou.