Within eclipse, with Subclipse installed, if I right click a project and select \"team\" there are normally 2 options:
Please double check if you were using: Subversive or Subclipse?
It is likely that you have opened an old project with a newer Eclipse installation, where the software to be used may not be the one used previously, for example:
In my case after a fresh install of "Eclipse IDE for PHP Developers" Version: 2018-09 (4.9.0) Build id: 20180917-1800 while I needed to make some modifications to an ancient SVN tracked project.
I had Subclipse instead of Subversive (so simple yet you may be up for a spin).
Credit to the answer from Yaniv, he had installed the software the other way around - same issue.