@DAH_99 

Unplug the extender and take it to the same room as the router and plug it back in. After the extender boots up see if the 5G light is now on. The 5G signal may be too far for the extender to connect to so the connection drops. If the 5G light does not turn on while in the same room, the factory defaults it by holding the reset for 15 seconds while it is plugged in and set it up again while the extender is in the same room. Leave the extender there to see if the 5G drops or if it now stays connected. If the 5G stays connected move it to the original spot. If the 5G starts to lose the connection move if closer to the router.

@Tony did unplug and 5G did appear but now when I select 5G on my device (IPad) it's says weak security). I went and selected the 2.4 and get same message.  When I choose original home network all is good.  I also did a network check on my carrier app and did give me a message I have an old repeater in my network and it only works on 2.4 band, limiting my speed.  Does this mean my extender is faulty?

@Tony  Also, today the extender's 5G light went out again - repeated above and moved extender to the room where router is and this time 5G light does not want to turn on.

@DAH_99 

If the 5G continues to go out I would reach out to support as there may be something wrong with it.

The weak security is from the new iOS update that no longer views TKIP as secure so you need to utilize AES in order for that message to go away.

There is firmware for the RE650 that allows you to set the security to AES: https://static.tp-link.com/2020/202010/20201012/re650v1_en-up-ver1-0-8-P1[20200922-rel60445].zip