Hi friend,
firstly I would recommend finding out why they stopped talking to you. You can try to send a text or note asking what was the problem and why you haven't heard from your friend. It may be hard to reach out to them if you haven't talked to them in a while. Try to start the conversation with something easy and don't go straight to the topic of why they stopped talking to you. Start the conversation first and then make an honest apology. Give them some time to think. On the other hand, if you didn't do anything that should apologize about, maybe just consider if you still want to keep this friendship. Friendships may be hard to maintain at times, but fights and conflicts are normal.
Thank you!
Dear Letterbox