More data needed! Arch pain is very unspecific.
E.g., when does the arch pain start? Immediately upon putting the foot in the boot? After and while you put weight on it? A few minutes after you start skating? Many minutes after you start skating?
Have you tried putting stuff under the arch - e.g., tape or adhesive foam underneath the insole, directly under the arch?
Have you tried putting stuff everywhere else - e.g., tape underneath the insole, everywhere but the arch?
Have you tried removing the insole?
Is the pressure of the boot all over your foot uniform? (Most people feel it should be light or non-existent next to and in front of the toes, but roughly equal everywhere else?
Are you using muscle to prevent the boot from edging to the inside? (Continuous excess muscle use makes you sore.)
Are you using muscle to prevent the boot from edging to the outside?
Are you using muscle to prevent the blade from rocking too far forwards?
Are you using muscle to prevent the blade from rocking too far backwards?
Is there a part of your foot that looks red or otherwise looks different after skating? (Maybe because your foot is slipping there.)