This is a tip to anyone having similar issue that me.
I upgraded my RPi to 4/4GB and all was working ok for some time.
At some point, i’ve changed the memory split to upgrade memory for GPU. After that my Aotec z-wave stick was not visible by the RPi (no /dev/ttyACM0 and nothing in lsusub ).
Found multiple topics on the internet that there are issues for this specific pi (4GB) to some improper memory handling. The solution was however patched into the kernel.
I try upgrades, lowering memory in boot/config.txt reverting the GPU memory allocation … nothing was working.
After hours of googling i found that the Aotect stick is very incompatible with USB specification (it refers to some power handling issues).
The solution was to connect the Aotect over some external USB Hub to solve that issue and it worked.
So if You search the internet for a similar problem and landed here, i hope the solution will work for You.
P.S.
This is rather a workaround - the only proper option i considered is to change Aotect stick to some other, but for now the above works fine.