As reported in a mattermost thread by @petednz, verified by my and summarized here:
Ext version: 1.9.0
CiviCRM version: 5.74.4 (possibly earlier versions; probaly later ones)
Repro:
-
Install and configure the extension so that a given contact (e.g. "Bob Cratchit") should have a working icalendar feed.
-
Confirm that Cratchit has a working feed by navigating to the contact's Contact Dashboard (e.g. example.org/civicrm/user/cid=n). This should (and does, in my testing) display a link to Cratchit's feed details:

-
Navigate to Cratchit's contact record, and open the Activities tab. Look for a link to feed details near the top of ths tab
Expected: Links to feed details should appear here, as in this screenshot:

Actual: The links do not appear, as in this screenshot:

Assessment:
Looks like a bug to me. Extension is making some assumptions that are incompatible with this (and probably future) core versions.
As reported in a mattermost thread by @petednz, verified by my and summarized here:
Ext version: 1.9.0
CiviCRM version: 5.74.4 (possibly earlier versions; probaly later ones)
Repro:
Install and configure the extension so that a given contact (e.g. "Bob Cratchit") should have a working icalendar feed.
Confirm that Cratchit has a working feed by navigating to the contact's Contact Dashboard (e.g. example.org/civicrm/user/cid=n). This should (and does, in my testing) display a link to Cratchit's feed details:

Navigate to Cratchit's contact record, and open the Activities tab. Look for a link to feed details near the top of ths tab
Expected: Links to feed details should appear here, as in this screenshot:

Actual: The links do not appear, as in this screenshot:

Assessment:
Looks like a bug to me. Extension is making some assumptions that are incompatible with this (and probably future) core versions.