Experience the following error in the Notifications Portlet after upgrading to Liferay 7.0. After further investigation, we were able to observe that My Workflow Tasks Notifications were not properly upgrading and were using the old portlet id of '153'.
Steps to Reproduce:
1) Startup Liferay 6.2 SP20 connected to MySQL
2) Navigate to Content > Documents and Media
3) Create a Folder and enable Single Approver Workflow
4) Create a new User with Administrator Role
5) Sign in with new User
6) Create a Basic Document in the created Workflow Task Folder
7) Observe that both Users have notifications
8) Run upgrade to Liferay 7.0 SP8
9) Navigate to My Account > Notifications
Expected Result: Workflow Notification will show created from Liferay 6.2
Actual Result: "Notifications is temporarily unavailable" error is thrown in the UI along with errors in the logs (npe-errors-testing.log).