request failed Error: Errors: sessionId query parameter is required;

[nicholase927171]

I have installed version 2.8.1  AT.js script  (not using Launch). The error I am getting is: 

"request failed Error: Errors: sessionId query parameter is required"

When I check the network request I can see that the sessionId is empty. However, the sessionId is available in the cookie? 

session#a2697fae040c457980a62a7cde5e651b#1646919668|PC#a2697fae040c457980a62a7cde5e651b.37_0#1710162608

How do I fix this?

Thanks

[alexbishop · Accepted solution]

I've seen this problem caused by one of two things:
i) If you were using mbox.js and then migrated to at.js, this can result in 2 mbox cookies being set, one of which has the correct structure that at.js is expecting, the other which has the old structure that mbox.js expects
-one solution is to add some code (i.e. within the tag manager) to check if there is more than 1 mbox cookie and then delete the mbox cookie with the "old" structure
ii) Also seen this issue be caused by using the old Visual Editing Helper plugin; again for similar reasons as mentioned above
-solution here would be to update to the latest version