What happens when you click "Dashboard->Wallets", then the (triple dots) menu of your Bitcoin wallet?
I just registered on Remitano to see how it works. In the following image, you can see the menu appears after clicking on the 3-dots button.
I couldn't find any option for seeing previous generated addresses.
Besides, their system won't allow you to generate more than 20 unused addresses. Probably, they set this gap limit so they don't have problems when calculating your total balance.
Yes, that's exactly how Remitano works. I clicked on "generate new address" button 20 times and now the button doesn't work anymore.