hey, i had the same issue and figured out how to make 4chan not block my ip. i used a proxy instead of a VPN. some proxies are less likely to be flagged. check out sites like hide.me or proxy-ninja for decent options.
also, make sure you're not using the same username or posting patterns. 4chan mods are sharp and can link your activity even if you change your IP.
also, make sure you're not using the same username or posting patterns. 4chan mods are sharp and can link your activity even if you change your IP.