> Is there something casuing this ...

It is pretty common today that sites protect themselves against bot traffic. Too much bot traffic might result in IP addresses getting a bad reputation for some time. Depending on how exactly the bot protection works it might also be at the level of the user account.

> ... i can fix?

There is no single solution which is valid for all sites since there isn't a single way of how bot protections work.

If the bot protection works at the level of an IP address you might try to connect from a different IP, like using a VPN. Sometimes ISP will also assign a new IP address when reconnecting the modem, but this depends on your specific connectivity. If the protection works on the level of some user account you probably need to wait longer.

>  Recently, i wrote a web crawler to visit that site and do things for me. 

Better read the terms and conditions of the site before doing this. Many explicitly forbid the use of automation against there sites and many enforce such rules, no matter how well intended (in your personal opinion) your use was.