For 2 weeks now, any new purchases I make from the market show as download on the website, but in Epic Game Launcher Library it shows as unavailable. I have spent over $1000 in new assets and I can not install any of them. I have reset the cache, I have checked my network, I have reset the launcher, reboot my machine. I see my payment history is there, my credit card has been deducted. I have selected various versions of unreal engine. This is not cool that I can not download and install the assets. I have uploaded images from the application and from the web. I have over 100+ assets I can not download from the Launcher.
Did anyone ever answer you about this after 2 years it just show your question but no answers! 
Did you ever find a solution to the 1,000 Asset Library Limit?
Thank you, sorry to revive an old thread, but… … ??
Hey I have this issue too. I’ve looked online and apparently one way is to completely close UE Launcher and then reopen. It may take a while as it update but then you should be able to download. However this has been working for some and not others. I am one of the latter and have opened a ticket with UE as its been more than 12 hours and no update in the Launcher.