Only this ONE... can buy anything else from this seller. Seller assures me it's not on his end. is selling dozens a day. I can't add these to my cart or buy in any amount... not 100, 200, 400 or 1,000! These are the error messages I'm getting...
You would think that a foundational feature, such as being able to buy something that is for sell on eBay, that the seller wants to sell to you, and the buyer wants to buy from you, wouldn't be an impossible task. I can't buy this from the seller, and the seller can't sell this to me. I've called customer support... supposedly a ticket has been put in... but day 4 and I still can't buy the item I want to buy on Ebay!!!!!
So how about one of you tech genius' figure this out for me and figure out how I can buy this... if not... how about you just tell ebay to buy it for me and ship to me. I Want to buy 1,200 of them with my anchor store coupon of $150 off. You'd think it wouldn't require rocket science to make this transaction. 🙂
Added 1000 to cart using browser on my phone just fine. Guess being a tech genius has its benefits. 
From your screenshots, it appears eBay thinks you have hit the set limits for purchases of that item for some reason. It is something that maybe should reset with time, but internal details of how those limits operate (x items/week, x items/listing run, etc and how/where the user data is stored) is unknown.
Since it appears to be you and not the listing (cookies, browser, account, karma...), I'd suggest changing the things you control:
Yep, the old "clear cookies and cache" I hate seeing as a general panacea may actually do something in this instance. If that doesn't do the trick, try another browser.
One other thing you could try is to add to cart using another account - if that works, it may indicate problem is account linked gremlin not a browser issue (but might not rule out cookie related causes). Not a solution because of the coupon aspect (unless coupon is transferable) but has diagnostic use.
Last wild idea is to sign out of eBay everywhere using
https://signinalert.ebay.com/sgninalrt/sessions
clear cookies/cache for a fresh start and see.
That's all the rocket science I can come up with at the moment.
From your screenshots, it appears eBay thinks you have hit the set limits for purchases of that item for some reason. It is something that maybe should reset with time, but internal details of how those limits operate (x items/week, x items/listing run, etc and how/where the user data is stored) is unknown.
Since it appears to be you and not the listing (cookies, browser, account, karma...), I'd suggest changing the things you control:
Yep, the old "clear cookies and cache" I hate seeing as a general panacea may actually do something in this instance. If that doesn't do the trick, try another browser.
One other thing you could try is to add to cart using another account - if that works, it may indicate problem is account linked gremlin not a browser issue (but might not rule out cookie related causes). Not a solution because of the coupon aspect (unless coupon is transferable) but has diagnostic use.
Last wild idea is to sign out of eBay everywhere using
https://signinalert.ebay.com/sgninalrt/sessions
clear cookies/cache for a fresh start and see.
That's all the rocket science I can come up with at the moment.
