Not entering Play Mode

When I press the play button Unity just blinks and doesn’t do anything.

FAQ :

What are the guidelines for writing good questions?

We want Unity Answers to become a comprehensive database of questions and answers related to Unity. When you ask your questions, it can be helpful to keep a few things in mind:

Don’t write things that will be irrelevant in a few days. Writing that “This is urgent!” will probably not get you faster answers, but it may make people frown at your question.

Some reasons for getting a post rejected:

There exists duplicate questions with answers if you were to do a search, either on Answers or on the Forum or on Unity's tutorials

Your question isn't specific enough: asking for a script, asking multiple questions in one post or asking a question that could be either subjective or require extensive discussion