Global Search not working in 7.8

Hi,

I have 2 version of sugarcrm installed in my server, version 7.6.0.0 and 7.8.0.0

ElasticSearch status is also green as well as the globalsearch in 7.6 is working as expected but on my version 7.8, the search always returns "No results we're found".

I'm not sure what I need to fix here. Can someone help me? -thanks!