Most cash drawer work through the receipt printer so firstly check your printer is working correctly. 90% of the time, we find the receipt printer has run out of paper.
If the receipt printer is working fine, then check if it's a loose cable. Check its in securely, push it in order to make sure. If that does not help take the cables out and put them back in.
If this does not ďes not fix the problem, consider asking for help, as a rule I would expect that there is a problem it is in your receipt printer not in the cashdraw.