You may try a different wall socket. If it won't work either, I think it is defective with power adapter or device itself.

I think if you use MR3040 without battery, the router could be pretty unstable to work.

I tried connecting the power from my laptop's USB port. Same thing happened. Is this considered defective? I wanted to use it without battery when I'm at home. To expand the battery's life. But sadly, it just keeps on restarting. Any fix? Thanks.

I have the same problem too. I want to save the battery life too.

I found that, if the device is working with LAN cable, then there is no problem without battery.

If we want to use the router as a 3G/4G router, or Wireless AP (Brige) , it can't work without battery. It will be kept restarting. Maybe there is no enough power to support the 3G modem or more transaction on the wireless.

TOO BAD design. I don't know why it can't support 3G/4G modem without battery.

I am from Indonesia

I also experienced the same thing. 3040 can not operate without a battery despite using the ac adapter. If I knew this I would be better off buying a 3020.

Newer 3G/ 4G modems are very power hungry (in excess of 750mA).

It is probable that this older router is insufficiently powered.

Cheers

John k