Following the rename of SharePoint last week, we've been made aware that the "Quick access" links to SharePoint sites are currently not working and resolve to an error message. Microsoft have said that these Quick access links will update over time to new versions but no timescale is known for this.
In the interim, you can add a shortcut to your SharePoint site into your personal OneDrive. This will take you directly to the SharePoint site and allow access. Alternatively, you can pin new SharePoint sites which will override the old broken links. Please see the attached guide for instructions.