You can try this
Exchange remote connectivity analyzer. I linked you to an article describing how to use the tool. The actual tool link is there in the article.
Going through that, it will show you what your org is giving you for autodiscover urls as well as the activesync url. It will require you to use your live credentials to test it. If you capture the outputs of the autodiscover and activesync tests, fully expanded of course - it should give us a starting point on to get you syncing again.