elgg1.9.7

Are you getting any specific error message?
Are you using any plugins other than the one bundled with elgg?

Are you sure that you use the correct admin username and password? Can you log in as another user or does the same problem happens then?

Same prbolem is with me?

any non-core plugins running?

Do you have PHP 5.5?

Check if the database is corrupted.

The easiest would be to strip the entire presentation layer, i.e. the view system, to make it work. But that will mean that plugins will have to be integrated one by one. You can of course write individual directives, but from past experience trying to create JS-driven apps in Elgg, it's a snowball effect - to get a page as JSON, you have to rewrite pretty much everything.

Evan did some work on this, but I think he hit a dead end:

https://github.com/ewinslow/ng-require

https://github.com/ewinslow/elgg-angular