Problem Huawei Y625 stuck on "Emergency call"


I received this phone the other day (Y625-U51 with Android4), I only used it a little on the Internet via Wi-Fi (Youtube), without SIM.
Today I inserted my Digi SIM, it worked for half an hour on GSM (data and voice), lost connection with the network a few times, then it worked fine. After I re-entered the Wi-Fi for a few minutes, then I left, the phone only displays the time and the phone keys and the message "Emergency call", in the upper left corner "Emergency call only". I removed the battery and the SIM, but it remained stuck in this state and nothing can be done with it (probably just call 112).
I don't know what happened to the operating system, it starts and goes into the "emergency" state. I can't get to the settings.
I'm not very knowledgeable in this field, I'm just asking if this defect/condition is known and what would be the remedy?
I know that the phone is morally and physically outdated (which is why I got it), it's even possible that Android 4 has problems with Digi (I replaced the SIM today at RCS because before I had a miniSIM and the Y625 works with microSIM, the SIM is OK, I use it in the old phone, with Android5).
Thank you in advance!