Intuit has indeed acknowledged that there are 2 issues with Intuit Link and that they're working on a resolution although there's no ETA for either.  You can find discussions of these issues here and in the PTO FB group.

• Intuit not loading, with spinning circle;
• Clients receiving 2018 invitation getting only access to 2017 in Intuit Link for Taxpayers

The first is more a performance issue that may be overcome by one or more of the following:

• Use an incognito window;
• Reload frame (where Intuit Link is supposed to load);
• Clear cookies/cache/history;
• Restart browser/computer/device;
• Use another browser/computer/device

The second is happening to some but not others and there doesn't seem to be any rhyme or reason, unfortunately, so, there's nothing you can do or not do to prevent this.

Intuit has also just restored the notification function so that you receive a daily report of your clients' activities.  You should check whether you have that turned on and have the right email address.