Problem with field showing up on custom invoice-Help!

Hi - I made an adjustment to my custom invoice template, and now have one field's content not showing when printed or saved as a PDF - but it shows on the record online.

I've compared the custom invoice fields to those on the standard invoices and cannot ( to my frustration) see any difference.
Not to the field name, or the the field syntax, or the field's placement.

Specifically, I'm having problems with %TaxValue% - the amount shows up on the invoice online, the tax amount is calculated in the Total (%InvoiceTotal%) - but I cannot get it to print the actual amount. It will only print " %TaxValue% ".....

I've attached one of my invoices where this is happening.