Hey, what is the led status of the powerline adapters? what is the speed you can get from the main router and the 4010Kit?

TP-Link has released an instruction on their website on how to do with the slow speed issue. https://www.tp-link.com/en/faq-2231.html 

You can follow it to narrow down the issue.

Speed is normally the maximum one: 100mb. I use fiber.

As I commented this is normally ok. Only some days I face this issue. I already tried those tips

Cause it happens occasionly, try to disable power saving mode and give it a go.

https://www.tp-link.com/en/support/faq/2018/ 

Download link for the tpPLC utility.

https://www.tp-link.com/en/support/download/tl-pa4010p-kit/#Utility

Finger crossed. 

PLC MODEL: TL-WPA9610 KIT

FIRMWARE: 1.0.1 Build 20170615 Rel.64685

HARDWARE: TL-WPA9610 v1.0

I have 600Mbps contracted and the maximum speed that I have achieved after many tests has been 110 Mbps only. I think it's impossible for these PLCs to take away so much bandwidth. I have followed the manuals to the letter, I have updated the Firmware and nothing. I do not know what may be happening.

what about the wired/wireless link speed and the powerline link speed showing up on the tpPLC utility? https://www.tp-link.com/en/support/faq/2265/

Try  to put them in the same room and do a comparison speed test. there is an instruction released by TP-Link.

https://www.tp-link.com/en/support/faq/2231/