@Sunshine 

Thanks, I tried the reset but to no avail. I even tried to reinstall firmware, but the upload failed saying the file was incorrect. (I double checked before attempting to upload). I am now returning the modem to the store as it is under warranty.

If the issue persists, it's advisable to contact TP-Link support. They may be able to provide specific guidance based on the error code and symptoms you are encountering. You can find support options on the TP-Link website. If the router is still under warranty and you are unable to resolve the issue, consider returning or exchanging it. Given that you just purchased it, the retailer or TP-Link should assist you with a replacement if the device is indeed faulty. Ensure that the Archer MR600 V3 is compatible with the frequency bands and network standards used by your mobile service provider (Vivacom). This information should be available in the router's specifications and your provider's documentation.