Hi Solguy123
Thank you for raising this issue with us and sorry it took so long for our support team to get onto it, it has been a busy few days!
The support team have now found that there is indeed a display bug which occurred when the game provider system of the game you were playing had a delay in sending us the result (it took over 20 seconds in this case) - and this resulting in your active promo going into a problematic state. When you returned to the withdrawal screen the bug caused the screen to show no available funds to withdraw (which is because you just had promo funds in this problematic state).
The team are currently working on a fix for this which will be pushed to the live system once it is thoroughly tested.
Once the bug is resolved, our support team will credit your account with the full amount of the Cashback you held at the time of the bug. We will notify you through the support channel or your email.
Best of luck at 8BET!