I'll try that on phone and iPad.
I have no difficulty with the same file on my computer. It downloads, and automatically opens in SU 2021.
I've had the same issue with at least half a dozen .skp files - all open correctly on my main iMac computer, but fail repeatedly and in the same way (download is only 833 bytes) on phone and iPad.
I've cleared the cache on iPad, closed and reopened Chrome, and tried the download again. Same result. Download says it's going to be 6.7MB, but it's still only 833 bytes.
Will cold reboot iPad and try again.,
Still no success. Tried several other recent and not so recent .skp files ranging in size from <400K up to >10MB. All, when downloaded via Chrome, come onto the iPad at 833 bytes and aren't valid Sketchup files.
Tried installing the Dropbox App. That will download the files to the iPad, but although I can see the downloaded file in the app, when I try 'Show in folder', double tapping on it does nothing, and I can find no way of opening it in the SU iPad app.
Still stuck on a valid way to share these .skp files between computer and iPad or phone.