Change IMEI on GL-E750 MUDI change IMEI EROR

I’m testing here around and found out that it’s possible to change IMEI on GL-E750 MUDI.

I do following steps
on the router UI, at “AT Command”

That works fine.

Then I put: AT+QPRTPARA=1 (Is this command is to save the new IMEI?)
And get this: “ERROR: Failed to execute command”

Who can help?

The following will hopefully help you to understand a tad deeper the idea but they are no written in stone.

Generally speaking the IMEI is written in the modem itself by the manufacturer and it is not intended to be changed by the end user. More often than not the IMEI is written in an OTP memory or a physical fuse is burnt after the process is done to avoid changing it.
In some cases, if you have access to service and debug tools from the manufacturer you might be lucky and get access to change the IMEI when it was programmed using certificate keys and not in an OTP memory or with a fuse burnt after the process.
It is a really nice pursuit the one you are following but it might end up as a rabbit hole.
If you want to play with changing IMEI for educational purpouses have a look at GerdaOS for KaiOS mobile phones as that allows you to achieve your goal and the platfom is based on Android and apps are not hard to write for KaiOS.
Last but not least, this procedure of changing IMEI is not legal in many areas of the world so treat this with care and again, my suggestion for KaiOS is only if you are looking at this from an educational point of view.