I am trying to transfer Blackbytes to another wallet I have on another computer but I can't. I've paired the devices but still can't. I've checked the Byteball wiki but I have found only instructions on how to trade Blackbytes with bots etc. The very simple issue of tranferring them I didn't find.
Do you have "normal" bytes in your wallet to pay the transaction fee to transfer the blackbytes?

That's right. You need to have very little "normal" bytes to pay the fee if you want to move your blackbytes. I experienced it myself not so long ago.