Hi Steinar ,
I think you are missing the coordinate the point for which you want to join by the line. The commands you have provided gives only the axes and line width of the axes does not change with parameter. For example, you may try the following for illustration:
>> FL=animatedline([1 2],[15 16],'LineWidth',5,'LineStyle','-')
as compared to
>>FL=animatedline([1 2],[15 16],'LineWidth',25,'LineStyle','--')
You may consider contacting MathWorks Technical Support of you region if you have more assistance.