I have completely the same situation - no chance to enable SSD Caching since both options are unavailable for me.
What I have:
1. AS3102T with the latest version of ADM (not beta, for sure).
2. One HDD and one SSD installed.
3. ADM is installed on SSD (have no idea if it is matter or not).
Here comes the screenshots!!!

- Screenshot 2020-05-06 at 13.14.08.png (68.81 KiB) Viewed 1119 times

- Screenshot 2020-05-06 at 13.14.26.png (116.97 KiB) Viewed 1119 times

- Screenshot 2020-05-06 at 13.14.37.png (254.38 KiB) Viewed 1119 times
So, I'm just stuck with SSD Cache being not able to select the desirable option.