Emergency calls only, no signal, device unlocked

Hi,

I having network issues with my Huawei P8. First of all it was locked to a network so I was unable to use other network provider's SIM card because it was asking for a network code. So I used one of those websites to buy unlock code and I applied it. Now it doesn't ask for network code anymore but I still have no signal and emergency calls only readings. So my guess is either IMEI is blacklisted which I checked on some website (not sure how accurate is that) and it came clean or SIM card reader is faulty. I bought it used so I don't know the previous history of it. I also tried to do factory reset as well as setting network operator manually (error was shown). So is there any way to find out that it is faulty SIM card reader for sure? Could it be defective main board as well? Thank you.