From HICC:

This is very likely the known issue with Housing Units, where a remnant of older code wasn't removed from the Housing Unit Controller, so it tries to load all Housing Units on page load; Once this exceeds a certain amount, the application starts throwing errors.

In order to allow the Housing Unit page to load, please go to the main page of HIFIS (done simply by clicking the HIFIS icon at the top left of any page). Then append this to the end of your URL: /HousingUnit/List?landlordID=77WWpWQ8nAZw

Depending on your website's structure, it could look something like this:
www.exampleAddress.ca/HousingUnit/List?landlordID=77WWpWQ8nAZw. (Not a clickable link, done for the sake of example.)

This address can then be bookmarked in your browser for easy access to this workaround. This will allow the page to load and the Data Table can then be used to asynchronously query for Housing Unit data in batches, rather than overloading the application limits by attempting to load everything at once.

Please Note :  this issue has been resolved in Version 61 of HIFIS that is planned to release later this month. Until then, this workaround should do the trick.