Dear @M.-_123,

I have a CPE connection to a remote site cca 1,5 km distance, I'm using an CPE510 as client and a CPE610 as ap , everything worked fine for cca 1 month  but now after some hours the cpe610 is not responding to ping  but it's wireless connection is  on ( CPE510 remains connected to it and shows signal information)  

May I know how you run the ping test? Do you ping the CPE610 AP from the CPE510’s Pharos page? Could you please show a picture of the Ping results? Are you able to get Internet access from the CPE610 AP?

As you mentioned that the wireless connection is on, do you mean that the wireless signal LEDs are lit up on the CPE510 Client? What IP address can you obtain from your network through the two CPEs wireless connection? Please ensure the front router or switch connected to the CPE610 works properly, besides, check the Ethernet cables in the setup and make sure they are in good quality.

Dear @M.-_123,

Hi,  actually the problem is with the old CPE510, I have checked from CPE610 side and everything works. Sad thing is that after 2-3 years of service all 4 units CPE510 have failed, and in the worst possible way, usually they did not respond and don't connect to network, then after reset they work for a short period an then caput. So this last CPE510 after reset connects to the AP CPE610 but no data is transmitted  but it's LAN function are active, the web interface is working and the led's are on .... 

We haven't received such feedback before, may I know the hardware version and firmware version of the failed CPE510?

For the case, we may need to do further troubleshooting to address the problem. TP-Link have local tech support in Romania, if possible, could you please contact the local TP-Link support via support.ro@tp-link.com for further investigation? 

https://www.tp-link.com/ro/support/contact-technical-support/#E-mail-Support

Thank you in advance for your cooperation and assistance.