Why would only a desk top PC keep losing internet?

I just installed T-Mobile home internet. I have a TP-Link router connected to LAN port 1 on T-Mobile modem/router.  I have a desk top PC (without wifi) connected via ethernet to the TP-Link.  Once a day it loses internet connection although wifi on both TP-Link router and T-Mobile remain active and 2 other devices connected via ethernet to the TP-Link remain active.  Those devices are T-Mobile LineLink and Tablo OTA DVR.  I can never get the desktop PC to reconnect without rebooting it.  Then it connects again OK.  I never had this problem with that PC when using that TP-Link router attached to Spectrum internet modem.

Any clues?