policy right - Run As Service - for windows service of search
add this account as Admininstartor - Go to CA > Service Applications > Select Search Service Application > in ribbon Permission > add account with full control
Hope it helps!
If search status shows as 'All Errors', there can be multiple reasons behind it. You can try following things to see if it helps:
Go to Windows services console and restart both SharePoint search service 15/16 and SharePoint search host controller one by one. Wait for sometime to see if helps.
Check in Central admin --> Application Management --> Manage ...
Is the issue existing in every file or a few files?
Try to troubleshoot this issue as following:
Make sure the search service application is actively crawling the content, and the files are crawled.
Please check if the following timer jobs is running, then re-run them and check again:
Microsoft SharePoint Foundation Usage Data Import
Microsoft SharePoint ...
The iFilter Shop sells and supports a variety of iFilters. If I recall correctly you will need to perform the installation and registration of the iFilter and then manually ensure that the Foundation SSA correctly registers the iFilter. In Server this is well documented, in Foundation, less so, though the folks at iFilterShop should be able to assist.