Localisation: GST/VAT worksheet programming guide

The liquid error is saying your code is trying to use a null (none existent thing) as an index to access a specific element in a data array.

The easiest way to find out how this could be happening is to print out the internal / intermediate values given your current Manager business. See the post above on debugging such as

More options are shown in that post or the Business information access post
Printing out some of the intermediate values may also help such as used in the code you added
A mistake in copying or changed UUID could produce this error