Vamos names the reason rather than failing silently. Each one means something different.
This account is private
Nothing can be read from a private account, on any platform, including your own. There is no workaround and no setting.
If it is your own account and you want Vamos to read your posts, the account has to be public.
This post no longer exists
Deleted or taken down. Vamos says so rather than inventing a description.
If you need it and you have it elsewhere, a screenshot attached to a chat still works. Vamos can read an image.
Videos only, we can't read this link
The link is not a post Vamos can parse. Usually a platform that is not supported for that action, or a page that is not a post at all.
Check Supported links and what Vamos reads from each for what each platform allows. Note that pasting into a chat accepts a much wider range than saving into a Collection.
That's a profile, not a video
You pasted an account URL where a single post was wanted. Saving to a Collection is one of those places.
Open the specific video and use its link. If what you actually wanted was the whole account tracked, add it to a Watchlist instead.
This is an ads search page, not one ad
A Meta ad-library search URL is a query, not an ad. Open the ad you want and use its own link.
If you want a broad sweep of a competitor's ads rather than one of them, ask in chat rather than saving links. Ad research runs live there.
Already in this collection
Not a failure. The item is there.
Nothing failed but nothing appeared either
If a creator was added and their videos are not showing, that is a scan rather than a link problem. See Why a creator's videos haven't loaded.