Please share the file you're working on.

The model seems to have been added ("icon.zip").

@dims12 You might try selecting both arcs and setting them to equal diameter "d". Once you do that I think the pair of arcs only has one degree of freedom, so each one independently has 1 right now and constraining the center point would require 2DoF for each arc.

When I do things like this, I usually make a construction line/circle. Then constrain arc end points to it and set their diameters equal to that of the construction circle, this avoids constraining the center point which seems to over-constrain in unintuitive ways. If you want coincident centers, another option is to constrain those first, then you'll also be less likely to run into this.