I have seen this SO MUCH both from myself delivering files, and from buyers trying to send me files.
The worst part (why I came here looking for this) is I got the “warning” from Fiverr threatening to demote my TRS level if it happens again.
I am fairly sure (but not completely) that they only go give these warnings if the buyer reports you. They may have done so unknowingly, but regardless, I did attach a file (it did not give me the usual question asking if I forgot to attach something) and Fiverr made it disappear.
Then they have the nerve to threaten their sellers over it. Disrespectful, ungrateful behavior from this website yet again.
Fiverr has no problem rushing in dumb features such as the widely-despised blind review system, but bugs like this that are integral to the site’s basic functions remain indefinitely with no action taken.
The worst part is that if they even looked at the order they would clearly see the delivery was not done to be malicious or falsely extend the delivery time, as Fiverr rudely states in its warning message. They would have seen the friendly delivery message, and this would indicate a problem on their end. But as I have seen many times before, Fiverr does not care about its sellers and are more than happy to send out these warnings without even investigating the problem.