I bought an MX4 Pro from an acquaintance. It worked perfectly with his SIM but will not recognize any new SIM apparently (tried 4, with at least 2 being latest generation). I always get a “no sim”.

I logged out of his flyme account, made my own etc. but it’s a no-no.

Is this a common occurrence? Any solutions?

In the meantime I put the international version on it, rooted it etc. To no avail.