If Basketball GM is refusing to allow you to play more, it could be because of a quota error. This happens when your browser decides to not let you store any more data because it thinks you're running low on hard drive space.
Here are a few things you can try to fix the problem:
If none of that works, you can try a Hard Reset which will delete all your Basketball GM data and leave you with a completely blank slate. Sometimes this is the only way to get Chrome working again due to this bug.
And if all else fails, you can try using another browser. Firefox works best.
If you need help, send an email or post to Reddit.