Chi square observed frequencies help please

Hi there

If anyone could help me , with what is probably a really simple/stupid question, I would be so grateful! It is not through lack of trying and reading to understand this- but I'm still really confused.

I have done a chi square 2x3, the assumptions were met as all expected frequencies were above 5, however for one cell the observed frequency was 0 (expected 5). Is it still possible to use chi square if this is the case?? I'm not sure if a Fishers exact test would be any better??

A significant result was found when I did do the chi square, and I also wanted to report the odds ratio but am I right in thinking it is not possible to calculate this if the observed count was 0 for one of the variables?

Any suggestions would be amazing and thank you in advance!