DHCP?? or .....?

1. A variety of devices always online (with wifi) lose access to the internet while maintaining a wifi connection to the router,

    The device shows connected (no internet) and resetting the device may or may not restore the connection. Meanwhile, the router (and a variety of other devices) maintain connection to both.

or

2. Various devices randomly cannot connect or reconnect to the wifi because "no ip is assigned" message received.  This happens whether a permanent IP address has been assigned, or DHCP is being used.  I have a DHCP range set above 2 or 3 permanent addresses.

Devices connected:

PC Windows 10  (cable or wifi)

2 x PC Windows 8 (wifi)

10" Samsung tablet

2 x 8" Samsung tablets

2 x S8 Samsung phones

Printer 

Garmen Scales

Google home hub

3 Google room speakers

Roku

ChromeCast

I've wasted hours reconfiguring, reading help files, resetting, etc.

Td-w9980_V1.160

TP-LINK RE350

(I unplugged the additional RE200, in case it was causing the problem)

HELP!!!!