I am so sorry to hear that you're unable to update it directly from your device. At this point, I recommend trying to connect your Tab S7 to a PC (if you have one) and download Smart Switch to update the device manually. I've located this article to assist with that aspect here please review while paying specific attention to the Software update via Smart Switch on your Windows PC or Mac section. - https://www.samsung.com/us/support/answer/ANS00077582/.
That absolutely should correct your update concern however if you require further assistance please visit a service center within your area using this link- https://www.samsung.com/us/support/service/ to proceed.
