MAC - OSX 10.10.5; Office 14.5.2

New load of Office onto new computer back in Dec/Jan so this is not a data file that has been building for years.

Yesterday, all was fine. Turned off and unplugged the computer late afternoon as we were supposed to have bad lightning storms. Started up this morning - everything seems to be ok. Started up Outlook and my task list is about half the size it normally is (and I wasn't that productive last night).

Everything else in Outlook seems to be ok - calendar is there, at quick glance my completed tasks (which I had to change some settings to view) are still there, Contacts look ok.  It just seems that half (maybe 60%) of my open tasks are gone. 

Doesn't look like any filters have changed - certainly I didn't on purpose. 

Have not tried anything yet besides restarting program, checking filters. I had bad experience with rebuilding Outlook on previous computers so I wasn't rushing to do. I do have a copy of the Office 2011 Identities file made two days ago as part of a general backup.

So should I try to rebuild, just replace the whole Identities file (or something else), delete a preference file somewhere, or ?????

Help please - I feel lost without the computer telling me what I have to do.

(PS: no syncing to a phone or pad or anything like that either - just turned off the machine yesterday, turned on this morning and had the issue)