Trouble sending an invoice from a Canadian address to an American address

[caand_uptf8]

 I am trying to send an invoice to someone in California but every time I try to send it I get the following message: 

There was a technical error - please try again in a moment.

I have read other people having the same issue and clearing it  up by putting the tax rate to 0.  Unfortunately the tax rate is non editable.  If anyone can help or provide a useful suggestion I would be grateful!

[roscobully]

Same problem here, I stopped selling on eBay for a while, now I know why.

[reallynicestamps]

You wouldn't be charging any taxes to a buyer in California. 
Only those in Canada, and even then only if you are registered to remit GST//HST/PST.

The customer will be charged California sales tax, but eBay takes care of that, not you.

Annoyingly, eBay does this by passing it through your PP invoice and you pay the PP fee on the sales tax as well as the selling and shipping prices.

Nobody is happy about this.