For the unmetered plans, you gotta whitelist at least one source IP (computer/server) via your dashboard to make the proxies work. You can whitelist up to 3 different IPs for each unmetered plan.
If you're dealing with websites that need captcha solving and using a tool like AYCD, make sure the source IP running the tool is whitelisted.
Also, if you're using third-party captcha solvers like CapSolver, you'll need to check with them and whitelist their server IPs.
Sometimes, certain bots/tools run your proxies server-side for the entire task, or they work with third-party captcha solvers and use their servers at checkout.
This can be problematic for the proxies because those third-party services need access to the proxies, but due to IP whitelisting, they can't access them and end up getting blocked.
Using unmetered plans can get complicated. Not everyone is tech-savvy enough to manage all this, and not all bots provide such detailed info.