Most of the time customer service won't do much, but they will still put you on a long hold before telling you that you're out of luck. I guess they want you to hang up during the hold. When actually talking to them, they spend most of the time trying to end the call.
If there is a problem like this, they may say it's a "glitch" and claim that they will report it to the right department. Do they actually report it? Did your call make a difference? It's not possible to tell because they normally don't followup with you directly.
Much of the time they will cite fine print from the site. There is fine print to cover everything, so this is always an option. They can say you were never invited in this case.
They frequently just blame you by saying you never tried to activate to begin with. This means they are calling you a liar.
Very rarely they will claim to take notes for your account AND at least promise to give you the benefits of a promotion for which you are eligible. They might tell you that it won't show up until the invoice, and if it doesn't, to contact them. By that time, you may have forgotten altogether. You really need them to email this promise to you and remember to check the invoice for the benefit. Most of the time you don't get any email. Unless you get it in an email that can be found in the eBay messaging system, it's your word against theirs. They will even look at your messages for the email and tell you that they don't see anything. You realize you're pretty much out of luck at this point. Much of the time they pretend they can't find any notes. You may have corresponding reference numbers, but most of the time they don't want them when you call back or can't find any notes with them anyway. Most customers people just give up at some point because all the effort doesn't seem to be going anywhere.
Everything depends on the amount of effort put forth by you and customer service, and the amount of effort warranted by you depends on the benefit. In this case, it depends on the amount you'd save if you sold the items under the promotion. If you are selling expensive items, you could save a lot. If you are selling dollar items, it's not worth any effort to get the discount.
