Version 5 of ActiveCollab has a whole new API. It is no longer possible to send the token via GET parameter. Instead, it needs to be sent in a request header.
This answer describes how to authenticate, obtain the token, and use it to make requests:
https://stackoverflow.com/a/34685298/338473
First request that you make during authentication will return all accounts that you have access to, and intent
that you use to authenticate with an account that you want to get a token from. This means that you need to know the ID of an account that you want to work with. When you know that, just loop through the list of accounts until you find the account that has the name
same as your ID. Use the url
for that account as a base for all future API requests (/api/v1/issue-token-intent
mainly).
Please check the answer that I already mentioned for exact commands and steps.