per our large customer:
"We opened a ticket the other night regarding API changes that appear to have occurred. We’re finding that nearly all of our in-house tools that make use of the Qualys API have broken. Some of the breaks we’ve seen so far:
1) session related issues, causing every call to create a session until we max out and get a 403 error
2) The String value “N/A” in DateTime Fields."
Note: I did not find anything obvious in the 8.10 API Release notes.