No VoLTE support on Max M2 for Vi/ Vodafone network

[digiwizkid]

Please tell us some basic information before asking for help:
Model Name: ASUS Max M2 (X01AD/ ZB632KL)
Firmware Version: OPM1.WW_Phone-16.2018.2011.78-20201127
Rooted or not: Not rooted
Frequency of Occurrence: Ever since
APP Name & APP Version (If your issue relates to the app):
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Asus Zenphone Max M2 (X01AD/ ZB632KL) is not supporting VI/ Vodafone VoLTE.
It does support VoLTE from Airtel on both the sim slot but not for Vodafone.
What is the reason for this? Anyone else also facing a similar issue?
Any possibility of resolution of this issue by a firmware update?
Thanks

[fussion_ASUS]

Hi, Please try the troubleshooting tips below:
1. Take out the sim cards> Insert the empty sim port to the end>Re-insert the sim port with sim card
2. Please try reset Network: Settings>System>Reset options>Reset Wi-Fi, mobile & Bluetooth
3. Please try to enter "Safe Mode". If the function works well in Safe Mode yet the issue remains out of Safe Mode, please check on any disturbance from the installed 3rd party apps.
# How to enter and exit "Safe Mode"
https://www.asus.com/support/FAQ/1005163/
4. Also, please try "the Factory Reset" after backing up all the data. 
Settings>System>Reset options>Erase all data(factory reset)
Please note that once the Factory Reset is completed, all data, apps, settings and personal information will be deleted.
5. If the issue persists after troubleshooting above, please check your SMMI test: Calculator> type ".12345+=">SMMI TEST>Single Test>SIM Signal Test
If any of the SMMI tests fails, indicating high possibility of faulty hardware, kindly bring your device to the nearest ASUS repair center for device checking: https://www.asus.com/in/support/Service-Center/India
If it is impossible to access the service center during Covid-19 period, please try Call us: https://www.asus.com/support/CallUs