Sorry maria, that's unfortunate you got an interview letter. Well that's better than an incomplete application at least. They sent an interview letter because they have concerns about your application. You should order GCMS notes to see what the specific reasons are for the interview.
https://atip-aiprp.apps.gc.ca/atip/
It's never too early for them to send an interview request, they probably sent it early because they spotted something very quickly about your application. My best guess is they are concerned about your parents not attending the wedding, you guys didn't have a wedding ceremony or wedding pictures. You should be prepared to wait approximately 12 more months for your interview, so during these 12 months you will be waiting, this is a perfect chance to go visit your husband again, spend more time together, maybe take a small trip together, take lots of pictures with his family/friends, etc. Basically you have 12 months to strengthen your relationship proof, and you need to maximize this time to its fullest. I don't know if your parents have changed their minds about not approving your marriage, but if they have, then it would be great if they could come with you on a family trip to visit ur hubby and his family, that would help a lot. VOs love it when they see pictures of one side's family hanging out with the other side's family, it shows you both are trying to integrate into each other's families.
If your parents are still the same old, same old, you'll have to give a strong and clear explanation during your interview, how they don't approve your marriage, hence they didn't show up, etc.