Hi @abhimittal496 , what kind of device do you have? Is your plan monthly or prepaid? Have you tried removing your Sim and restart your device, then shut it down again, then replace your Sim and start it up again? What sms app do you use? Try a different one with mms enabled. There are numerous reasons for sms not sending, I personally used to use the Samsung messaging app and ran into this a lot. I changed to Google messenger and enable rich text messaging and it has been good ever since. Depending on your device, other fixes may be required. Like different 3rd part app or stock app. Without knowing what device you use, I only have Samsung remedies
