Some badly-coded websites do not perform as expected with the iPadOS Safari User Agent operating in one or other of its browsing modes - of which their are two - these being Desktop and Mobile.
It’s easy to switch between modes if a website isn’t functioning correctly. From the desired web-page, touch the aA icon at the left of the Address Bar; this will reveal a menu. From the menu select Website Settings, then select (or deselect) Request Desktop Website, then tap Done. Now refresh the webpage.
The chosen setting will be saved for the selected website - and can be simply reversed if needed.
Problems can also arise if you are using an Ad or Content blocking App. If using an Ad-blocker, try temporarily disabling the App - or modify its ruleset to white-list the website URL that is causing difficulties.
As a last resort, try using an alternative browser App - such as Firefox:
https://apps.apple.com/gb/app/firefox-private-safe-browser/id989804926