Serial number not recognised/ Scrivener not opening

The advice in that link is no longer valid. Because eSellerate became unavailable as a vendor, L&L had to switch e-commerce partners. Unfortunately, one of the resulting changes was:
[attachment=0]94C972DD-3237-4F66-BDDC-08F0F8C20013.jpeg[/attachment] … hange-list

As xiamenese suggested, contacting L&L support would be best to sort a licensing issue.

If maliklentera can’t install Scrivener 3, doesn’t that imply that they are using an OS version (10.11 or earlier) covered by the free 2.9 version of Scrivener?

Scrivener 2.9 no longer even asks for a license key. So unless they’re using an old download – before the switch from eSellerate – it should “just work” with Mac OS 10.11 or earlier.

If they’re using Mac OS 10.12 or newer, they should install Scrivener 3 and contact support if it fails to work.