There is no limit to the number of terms you can have linking to a target page/URL, however, what happens is, if you have 10 keywords all linking to the same page/location, and more than one is on the page, SEO Ultimate will choose one to link.
You can overwrite this functionality in the Deeplink Juggernaut (Content Link Settings) area and specify [x] Don’t link the same anchor text any more than _X_ times per post/page/etc. Just add the number you want. One is ideal, since you don't want multiple links linking to the same destination (from an SEO perspective) but perhaps for users its ideal, depending on your situation.
Also, I did notice on some blog configurations that if I clicked the [x] Enable per-link customization of quantity limits in the content link settings area in version 7.5.7 that the autolinks functionality disappeared (which is what I believe happened to you).
This is a bug which we will address in the next update as per link customization feature (allowing you to cap the number of total links built per keyword) worked fine on previous SEO Ultimate versions.
So, to remedy this, make sure you do not click the [ ]Enable per-link customization of quantity limits and your links / auto links should reappear.