Intermittent connection issues via LAN cable

[ALW99]

After finding the wifi signal wasn't stable enough to work from home I bought a 15m Cat 8 ethernet cable and ran it from my router to my home office. Generally worked well for a few weeks but now when I try to go online each morning on my work laptop, any website comes up with unreachable and needs a reset (turn it off, turn it on again) of the router to clear the issue. Wierdly, outlook and team's messenger load fine and update, so some traffic is getting through. Just plugged my personal laptop in this evening and have the same issue.