While working with Gantt Cloud add-on you may encounter an error message which looks similar to this one:
It usually means that in some project the following scenario occurs: Issue A -> (blocks) Issue B -> (blocks) Issue C -> (blocks) Issue A. In such case, there is no clear way to visualize such dependency chain on the gantt chart and therefore rendering engine will report the error above.
One of possible solution is such case is to filter out troubling issue(s) or even entire project. You may also reconsider how the links in your project are created as having such dependencies might not be a good idea anyway (for example, you may want to use "relates to" links instead).