Follow the rules of the actual assessment, not the assumptions in third-party practice material. Your preparation should match the conditions you will face on test day.

A practice resource can still be useful for the question style, but using tools that are not permitted can hide a pacing or arithmetic weakness. The official instructions are the source of truth for allowed resources.

If the real assessment prohibits a calculator, redo some representative practice sets manually even if the original practice platform provides a calculator button. That gives you a more realistic view of your speed.

Review the official test instructions, recreate those conditions in practice, and focus on shortcuts, estimation, and clean written setup where calculators are not permitted.

Official test rules win. Practice sites can be totally different.

I'd switch to manual now so test day isn't the first time without a calculator.