Unable to install iOS 17 on my iPad Pro

The oldest iPad 12.9-inch that will run iPadOS 17 is the iPad Pro (12.9-inch) (2nd generation) (Wi-Fi). That corresponds to model number A1701. Your model number is in painfully tiny print on the back panel of the iPad. If it is less that A1701, your iPad is too old to update past iPadOS 16.

...if this is not resoved I will not purchase another apple product

Fine by me. Apple will not see threats in this user-to-user forum. eBay sets its operating system requirements, not Apple. Your ire is misdirected.

zedzoirer141 wrote:

I cannot download ios17 on my iPad Pro (12.9-inch) and because i can't I cannot use eBay if this is not resoved I will not purchase another apple product

If this is a first-generation 12.9" iPad Pro – a model that ran iOS 9.1 when Apple introduced it over nine years ago in November 2015 – iPadOS 16 is the end of the line. You need a second-generation one to update to iPadOS 17, and a third-generation or later one to update to iPadOS 18.

As far as threats to "not purchase another apple product", this is a user-to-user forum, and such threats don't carry any weight here.

Since iOS 18.x is the latest version and your iPad can't even update to iOS 17 it sounds like you own an older iPad. If that's the case you can only download the latest version of iOS that is available for whatever model of iPad you have.

If eBay is blocking you from making purchases then it's likely due to it being an old iPad with less security features for making online transactions.

If it's none of that then you need to explain in further detail what's going on.