Same problem here. Does anyone from tp-link monitor this board? Can someone please address this problem with some real solutions! 

@entsurv nobody responds here it seems, they've stopped responding to my messages altogether, so thanks for jumping in. mine has continued to disconnect every few days and only a cable modem and router reboot fixes it. no firmware updates from them in the past month or so. this is my third ax21 router all have the same issue.

@glf I was on a call with tplink tech support and they apparently had no more idea than you or I what the problem is. A complete reboot/reinstall "solved" the problem temporarily (which is what tech support suggested) but it didn't take long for the problem to reoccur. I'm looking for a different router with better LAN reliability ratings, but its hard to find good information. All wireless, no ethernet.

I'm having the same problem with the same router.   Dropping all Ethernet clients. Various reboots now will not get them to connect at all.  
 

Rather frustrating. 

@glf 

Are you using the power adapter that came with the router? 

Be sure the eithernet cables and the connectors are in good condition. May want to try different ones.

Also if you have USB devices attacted, try without them to see what happens as if they pull to much power that causes strange issues. 

@ArcherC8  Why would evrything work, ethernet and wi-fi, for weeks and then suddenly all ethernet ports stop functioning? This is not a power supply/cabling problem. I have reinitialized the system by resetting the router to factory defaults, and can bring the entire system back to life, FOR A TIME (days-weeks) before the router craps on the ethernet again. 

@ArcherC8 

Are you using the power adapter that came with the router?

yes, have done that with each router so far

Be sure the eithernet cables and the connectors are in good condition. May want to try different ones.

All my cables are farily new and in excellent condition, and all within a few feet of the router. 

Also if you have USB devices attacted, try without them to see what happens as if they pull to much power that causes strange issues.

No USB devices have been installed up to now.

@glf 

Be sure the router is getting plenty of air as heat can affect the router performance. One poster raised his/her router so it had more clearance under the router and solved their issue.

@ArcherC8 my router is sitting on a shelf by itself nothing else is near it, plenty of air flow in a large room, and its sitting on the feet that it came with. what did the other poster raise theirs with? if something like that is needed then that's a manufacturers defect.