Here are different ways to solve for your problem:
- Check the APN configuration (SMS/MMS>MMS tab) and try to run a diagnostic (under "Assistance" menu)
- Check your SMSC settings if you receive SMS but you cannot send them :
- Open the Phone application.
- If the dialpad does not appear, tap the dialpad icon.
- Type *#*#4636#*#*.
- Tap Phone information.
- Scroll down to SMSC
- Tap refresh, check the number is correct (if not, contact your carrier)
- Copy the SMSC field and put the value in Mood>Settings>SMS/MMS>SMS tab>Set SMS Service center (activate it then put then value)
- Check you are in a spot where data is available
- Check you have enough mobile data or is it activated
- Go to Settings -> SMS / MMS -> MMS tab -> try decrease the operator's send limit value to 200kb (which is 300k by default), delete the failing picture in the thread and re-select it (to apply the new compression rate)
- Go to Settings -> SMS / MMS -> MMS tab -> try to check the GIF size limit to 400kb
- Check the sending method in "Media & Emoji" > Media tab > Select sending method for pictures & videos > Use MMS
- Try with a différent User Agent value in SMS/MMS -> MMS tab -> User Agent
- The MMS can take some time to be sent and due to potential Doze restriction and if the app is in background the MMS may not be sent (see below)
- Try turning off the WIFI completely and keeping only the mobile data
- Try to turn ON Settings>SMS/MMS>MMS>Disable wifi while sending or downloading MMS
- Try to restart the phone one or multiple times
We invite you to re-check that there is no warning in Mood in the "Assistance" and "Notification" settings. In particular, allow Mood to run in the background and not be paused by Doze mode.
In order to allow Mood to run in the background, I also invite you to consult https://dontkillmyapp.com which provides all the necessary procedures.
More radically there is also the complete deactivation of Doze on android with the command "adb shell dumpsys deviceidle disable" (via adb - not rooted) or to automate it on the phone with for example the Script Manager app from devwom (root required)