I didn't get a response from the last user with this problem. Are you using Firefox, or some alternative build, like Waterfox? If you open an issue at https://github.com/pdf/kdeconnect-chrome-extension/issues we can try to find out why this doesn't work for you, but I cannot reproduce this problem on my end.
I have published a new version of the extension (v0.1.4) that should appear on this site shortly, this has some improved error handling, so you may get a more descriptive error message if something unusual is happening.
Please feel free to open an issue on the Github repository (https://github.com/pdf/kdeconnect-chrome-extension/issues). The only time I have heard of this was from a Waterfox user, and apparently installing the extension in Firefox fixed it for them on Waterfox for some reason.