ebay.com and ebay.co.uk seem to be working fine for me in multiple browsers.
What page are you having problems with? If one or two specific pages are the problem, try holding down the shift key and reloading the page. If many pages are not loading the page format correctly, you may want to clear your browser cache. Be sure to select "All time" if that is an option -- some browsers like Chrome may default to "the last hour" which will not clear your older files. Try a private or incognito browser window, or try deleting eBay cookies.
If you are using Firefox, try disabling Enhanced Tracking Protection on eBay. That has caused similar issues in the last couple of months. See here:
https://community.ebay.com/t5/Technical-Issues/eBay-is-only-blue-text-with-a-white-background-AND-OF...
Not sure if Chrome has an equivalent feature.
If you have any browser plug-ins or add-ons such as ad blockers or script blockers that you are using in both browsers, try temporarily disabling.
You may want to try installing an entirely new browser as a test; that is often easier and quicker than checking all of your browser settings. If the brand new browser shows the same problem, your browser settings are likely not the issue -- then you may have to look to other common things like network problems.
Are you able to see eBay pages load correctly using your phone's browser when on the same WiFi network?
If your eBay works on your phone but not your desktop on the same network, see if you have any firewall settings, proxy settings, or VPN settings on your computer that might be causing an issue for you.
