Incoming call from PSTN not picked up by GXW4104


I bought a GWX4104 and set it up to connect to a local 3CX PBX running on oracle virtualbox VM. Occasionally incoming calls from PSTN were not picked up by GXW4104 and ringing indefinitely. When this kind of no pick up incoming calls happened, I login to the web admin portal of my GXW4104. Then suddenly after successful login, this action seems to resolve the no-pickup problem encountered and following incoming calls were routed to 3CX’s digital receptionist normally until next time no-pickup happening again.
Did anyone encounter this kind of issue before? Any suggestions and or directions point me to a resolution is appreciated. Thanks in advance.