User can't access Shared Calendar in Outlook 2013 (Exchange 2013 environment)

Hi there, we have a user (Bob) who is leaving the organization and needs to transfer a calendar** to another user (Alice)
**not his actual calendar, but an extra calendar he created and was sharing with the team

So what I did was:

1. Exported the calendar to a pst file.
2. Created a new calendar for Alice in Outlook.
3. Imported the pst in the calendar created at step 2
4. Sent a Shared Calendar invite to a total of 4 users (including Bob so he could keep editing until he leaves for good)

The problem is that the newly created Shared Calendar seems to work without any issue on Alice's account as well as the 3 other users to whom it was shared at step 4, but when Bob clicks on "open calendar" from the mail invitation to the shared calendar, all he gets is "the operation failed". Bottom line is the whole team has access to the new iteration of the shared calendar but he can't access it.

At first I thought that it was because he still had the calendar that was exported opened in his account but the issue remained even after removing it. I'm thinking it has something to do with the fact that he was the one who originally created all items contained in it but I can't come up with an explanation nor a fix.