Learn how to handle rejection and learn fast. Part of becoming an adult is accepting that you will not always receive a “yes” to every request you may have.
Other people have the right to say “no” to you. Throwing a fit, threatening, and/or harassing someone because you didn’t get your way is NOT healthy behavior.
If someone says they don’t want to RP with you, don’t push it. Don’t guilt trip them. Don’t ask why.
Say “Thank you for your time” and move on.