Symptoms:
- I am using Floating Licenses or Build Server Licenses.
- I am attempting to open a project using 2018.3 or older, such as 2017.4 or Unity 5.x.
Cause:
To utilize a floating license or a build server license, Unity Editor 2019.4.27f1 or later is required to use.
Resolution:
It is recommended that you upgrade your projects to at least 2019.4.27f1 in order to resolve this issue.
If this is not possible, please contact your sales representative about acquiring licenses specific to these older editor versions.