Solutions:
1. Whether function"always receive MMS" has been turned on or not.
2. Reset the access point APN.
Settings-mobile network-access point APN (for single card phones) / settings-dual cards and mobile networks-select the corresponding SIM card-access point APN (for dual card phones, the network card in the dual card phone can change the APN. If there is no change option, please change the network card first)
3. It is suggested to contact the local operator to obtain the SMS center number, enter Settings >> system application >> SMS > advanced settings >> set the SMS center number >> change it to the correct SMS center number.
4. Check to see if the third-party security software is installed in the phone. If so, uninstall and restart the phone.
5. It is suggested to replace the SIM card of a different operator and try again.
6. It is suggested to back up the data and restore factory settings, upgrade to the latest system version, and try to send again.
7. It is suggested to go to the local after-sales center for inspection.