Tax liability -urgent question- thanks!

[Sue Jing]

I am currently doing 1031 exchange, and looks like we won't be able to close one of the properties we exchanged. The 180days closing deadline is next week.  It's a long story, how we get to this point. 

My question is, for the capital gain we get with this exchange, Can you claim the loss we had from previous yr and the other properties against it to decrease our tax liability? Do it matter if we are considered as real estate professional? 

Thanks for all your response!