If you have posted a picture with a comment and hashtags to Instagram and only the images is published on the network, you might have used too many hashtags.
Please, go back to your Blog2Social one-page preview and reduce the number of hashtags you have used before.
Although, Instagram has not limited the character count for its posts you can currently only use up to 30 hashtags in your comment or caption. If you use more than 30 hashtags, your comment will not be posted.
Source: Instagram Help Center
If Instagram still doesn't publish your caption click here: Solutions: Instagram doesn't publish my text