Hello,
May i know on what operator its not working Cosmote Greece or Vodafone ?
Are you using both the mobile antennas provided . Its highly recommended to use both the mobile antennas.
I see in the troubleshoot file RSRP value is poor and at this value of -105 there will be disconnection :
AT+QENG="servingcell": +QENG: "servingcell","NOCONN","LTE","FDD",202,01,311701F,189,3194,7,3,3,1020,-105,-9,-80,17,-
https://wiki.teltonika-networks.com/view/Mobile_Signal_Strength_Recommendations
Have you tried using the same sim card in your phone or other device just to be sure if it has enough data in it?
Please let me know.
Thanks