If you can't find posBoss on the App store, there are 2 possible scenarios:
You aren't using an iPad - posBoss is only compatible with iPads, not tablets
Your country settings may not be set right.
How to change your iPad's country settings:
On your iPad, open the Settings app.
Tap your name, then tap Media & Purchases.
Tap View Account. You might be asked to sign in.
Tap Change Country or Region.
Tap your new country or region, then review the Terms & Conditions.
Tap Agree in the upper-right corner, then tap Agree again to confirm.
Select a payment method and enter your new payment information and billing address, then tap Next. You must enter a valid payment method for your new country or region.
A few other errors that may be due to the wrong iPad country settings:
All the items on your posBoss app till are set to $0
Your cash up dates show the wrong date in your reporting on the Management Site
When you cash up on the posBoss app till, the app crashes