Firewalls on your end mess with various parts of Steam. I have mostly seen it uploading screenshots because I don't use the market too much because I can recall a couple times seeing the errors there also. So, without knowing anything more I'd guess there's a pretty aggressive firewall on your modem or your router.

Most ISP use shared IP addresses for ipv4, so the ip address assigned to you, has multiple users on it, and some besides you, must use steam. So anyone with that IP Address who uses steam in the same time period, is tripping the IP rate limiter. Too Many Page Requests from the same IP address. This was put into place to stop browsers with add ons, Browser bots, and requests from 3rd party skin / item sale websites, that can send multiple page requests to the steam marketplace.

Only thing you can do is request a different / static / personal private ipv4 address assigned to you, or switch to ipv6 addresses if your isp has them available.

If your ISP supports ipv6, then turn off ipv4... This will also help solve the problem.

to see if your ipv6 is active go here:

https://test-ipv6.com/