Firstly, if you are able to download videos other than YouTube, it means that the Downloader is working right. We have seen from time to time that YouTube blocks users from downloading videos. Especially during this pandemic where the traffic is quite heavy, they throttle their bandwidth.
The only solution is for them to release bandwidth to your IP address. One way to fetch a new IP address would be to contact your ISP. You can ask them to provide you with a new IP. They can flush the IP address and send you a new one.
Since YouTube is throttling, there is little that we can do.The good news is that they are pretty good in providing more bandwidth sooner. However in some case it may take a couple of days.