It seems the Confluence team has merged the issues for the major supported add-ons back into the Confluence (CONF) project itself, see the components that start with 'Add-on - ...', e.g. Add-ons - Confluence Questions.
I don't know about the rationale behind this move, but while there are the usual oversights like the Submit a support request on the Questions for Confluence Marketplace listing still targeting the deleted project, as well as a slight loss of information (notably the former components), the issues as such are still available.
Any links to the former issues should simply redirect to the new one accordingly, see e.g. the infamous https://jira.atlassian.com/browse/CQ-361 (the JIRA issue macro here targets CQ-361, but retrieves and display the new issue key at runtime).
Accordingly, you can still access your watched issues from your profile as usual, though they will show up with a CONF key - finding e.g. all 'watched and open' issues can be achieved via a resp. JQL query as follows:
key in watchedIssues() AND project = CONF AND component = "Add-ons - Confluence Questions" AND resolution = Unresolved