Solved it. Apparently, for checkSession to work, urls in Allowed Web Origins MUST NOT end with /.
So, https://xxxxx.mydomain.com is correct, but https://xxxxx.mydomain.com/ is NOT
Solved it. Apparently, for checkSession to work, urls in Allowed Web Origins MUST NOT end with /.
So, https://xxxxx.mydomain.com is correct, but https://xxxxx.mydomain.com/ is NOT