1. Problem
2. Solutions
Finally, I found that each unity version has a package manager, which is the path in the picture, and they are all the same path. It is just because there are more or less small differences in different versions. Other versions can start normally, but 2021 can’t. Could it be that there is something wrong with the 2021 package manager folder? With a try mentality, I first replaced the UnityPackageManager.exe of 2020 into 2021 and found that it still didn’t work, and then copied the entire server folder to 2021. Go to the Server folder and then it can start normally. .