Can you first try logging in via the below website instead:
https://www1.advendapro.com.au/
Using your Campaign Cloud username and password on this website should log you in with success.
Alternatively, you can try clearing your browser cache.
Sometime the system will have trouble signing you in if your previous session times out or was closed down using the browser X instead of the 'Logout' button.
I have left some steps below on how to clear your cache using Google Chrome:
1. On your computer, open Chrome.
2. At the top right, click the three stacked dots.
3. Click More tools and then Clear browsing data.
4. In the pop up, choose the time range 'All time'.
5. Tick on the checkboxes next to 'Cookies and other site data' and 'Cached images and files'.
6. Click 'Clear data' button.
7. Close down your browser.
8. Re-open your browser and attempt to login again.
After following the above, you should be able to login without issue.