The built-in UPS shipping won't work anymore. We have
removed it from the OpenCart 3.0.x.x branch.
We have been trying in vain to set up a developer account with UPS for over a month, UPS has a serious bug in its card payment verification for credit cards, and it's support hasn't been of much help so far. Without a UPS developer account, it's next to impossible to implement and test required changes for the OpenCart core UPS shipping extension. If there are any users affected by it, I am afraid the only option will be using one of the other 3rd party commercial shipping extensions, more details on this can be found further above in this forum thread.