Outlook.com shared calendar disappeared for one user

I have a similar issue. Since a few weeks ago (2? not sure, could tie in with the Microsoft update), I can no longer edit a shared calendar that my husband set up a few months ago. Used to work fine. When trying to edit, I get a message 'You cannot make changes to contents of this read-only folder'. We checked my 'Sharing Permissions' for the shared calendar, I still have a 'Can edit' setting, but obviously something is veto-ing me ;S We tried to 'Remove' me from the 'Currently sharing with' and re-granting access. I get the invitation in Outlook, I accept, but same problem, I still can't edit. I tried creating a new shared calendar my end, granting edit access to my husband. Same problem occurs as above. The access privilege shows as 'Can edit' but it doesn't allow edits... Please solve quickly, thx :D! By the way, we are still using the Outlook Classic version as it suits our needs.