If you've been experiencing problems in the last week using the 'old style' Irish Civil Registration Indexes on the Family Search site, you're not alone.
It's gone 'wobbly' again. If you get past the intermittently frozen screen and/or semi-permanent clock/timer, you're likely to find no filters are available for your search and finally receive a 'no results' notification. Must be the season... It went 'on the blink' in April last year, too. It took several weeks to fix it and some would argue that it's never worked as well as it used to, ever since.
Of course, there is the option of moving over to the 'new style' Indexes collection but that's not behaving itself brilliantly, either! This is, however, the route that Family Search would like us to take. They seem determined to force us to make the switch, like it or not (and there's a lot of us falling into the NOT category). The new site simply doesn't offer sufficient opportunity to refine searches, and thereby narrow down results.
Apparently engineers are trying to resolve the technical problems.