This issue was originally posted here.

I had the issue and I resolved it with these steps:

1. Install tpPLC application to your computer. https://www.tp-link.com/tr/support/faq/1608/
2. Download the latest firmware files from here (be careful selecting the correct device version, V1 in my case.)
3. Upgrade firmware to latest in tpPLC app as it was told in instructions.
4. Turn off Power Saving Mode.
5. Set "Traffic type priority" to "Internet"

I hope this helps. It worked in my case.