Hi @benYNDLT,
I hope this message finds you well. The key here is to make sure that the polygon, the trace, and the via have the same name. In Fusion 360, connections are defined based on net name.
So use the NAME command to rename these items and make sure they have the same name. Once you do this the polygon will connect to those items.
Best Regards,

Jorge Garcia
Product Support Specialist for Fusion 360 and EAGLE
Kudos are much appreciated if the information I have shared is helpful to you and/or others.
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