Nick here from Shopify.
Would you be able to link the form you are trying to fill out, please? I just want to be sure it's the correct one.
Would you also be able to screenshot the error message which is showing up for you when you try to put your institution number in to let us know what you see on your end as it would be hugely beneficial in troubleshooting this and see what is going on?
Looking forward to hearing from you.
All the best, Nick