Why is my lg g3 d851 not reading my sim or letting me into apn settings?

[Jrbas69]

I bought this phone on line and it was rooted. It was running on tmobile previously. The rom on it now is dirty unicorns. I have activated a straight talk sim and installed it but it's not reading it. Also I try to get into the access point to change apn settings and it's grey and can't get into it. Is it something with the operating system or the phone?

 

[belodion]

I bought this phone on line and it was rooted. It was running on tmobile previously. The rom on it now is dirty unicorns. I have activated a straight talk sim and installed it but it's not reading it. Also I try to get into the access point to change apn settings and it's grey and can't get into it. Is it something with the operating system or the phone?

Welcome.

Is it locked to T-Mobile? The rooting and romming will not have had any effect on that.