I've installed a point to point system using 2 CPE210. 

The system is setup as follows:

ISP Router > CAT5 cable to TP-Link Router in holiday cottage > CAT5 to CPE210 AP > around 100m distance, clear line of sight > CPE210 Client > CAT5 to TP-LINK TL-WR841N

When I set the system up initially, it appeared to work. However, the customer called me back saying it had stopped working.

I took the equipment back to the office. When setting up in a test environment without changing any of the settings, the point to point link and router worked fine.

When I took it back to the customer, it did not seem to work again. It was able to connect wirelessly to the access point (using WiFi), while connected to this access point I was able to connect to the client using it's IP address. I was also able to connect to the internet. This suggest the 2 devices are connected.

Any ideas what can be wrong?