I have some changes checked in for the next JFBConnect release for Kunena 5.x support. I just checked Kunena import on my Joomla 3.6.5 test site with Kunena 188.8.131.52 and the avatar was imported correctly and showing in the SCLogin module for me.
It's possible that the errors that I fixed are causing the avatar import to fail, so could you tell me what you have for the following settings:
* SCLogin > Login View Settings > 'Registration Component' setting
* SCLogin > Logout View Settings > 'Enable Profile Picture' setting
* JFBConnect > Profiles > Kunena tab > 'Always Import Profile Data' setting
* JFBConnect > Profiles > Kunena tab > 'Import Avatar' setting
Also, are there any PHP errors in the JFBConnect > Profiles > Kunena tab area for you?