You hit an API quota limit. This quota limit is IPv4 based. If restarting your router doesn't help, you'll have to wait it out.

IPv4 addresses are not unique anymore. As there are more humans (8 billion) than IPv4 addresses (4.2 billion), ISPs have chosen to route users together on an identical IPv4 address. This technique is known as CGNAT.

For Valve's community market API this bundled together group of users looks like a single user.

If you waited several days to weeks, your only recourse is getting a public IPv4 address. It doesn't matter whether this one is static or dynamic.

Same here...