I'm trying to add a project ref to my main solution but unable to do so. I tried: Manually adding it from references option but the dll was not found. Changed the target version as well but no effect. FYI both projects have the same target version. Tried reinstalling VS as well.
Are there any other way to achieve this?
Right.
If they are in different solutions (and repositories) I recommend using nuget packages instead so you would dotnet publish yourproject and then push those packages to a nuget.org, a private (locally, something like C:\localnuget folder) or a private feed (gitlab, github and such).
If you don't have that scenario you would be better of adding the projects to your solution instead of adding DLL references. You will be able to keep them updated without the need of recompiling everything each time you need to change something.