Write a macro for license key or plugin activation issues

Tickets like this arrive constantly:

"I'm trying to activate my license and it says 'Invalid License Key' even though
I copied it straight from my purchase email. Please help."

Write a troubleshooting macro a support agent can send for this exact error,
working through causes in order of likelihood, not alphabetically.

Requirements:
- First check: whitespace or hidden characters from copy-paste. Ask them to
  retype the key manually instead of pasting it, this alone resolves a large
  share of these tickets.
- Second check: whether the license is already activated on the maximum number of
  sites allowed on their plan. Tell them exactly where to check and deactivate an
  old site (a staging copy is the most common culprit) themselves.
- Third check: whether their site's server can reach your license API at all
  (some hosts block outbound requests). Give a one-line way to test this without
  needing technical background.
- Only after those three, ask for the license key and the exact site URL so an
  agent can check the account directly, and note plainly this means the customer
  is sharing account access info, so confirm it's really needed before asking for
  it.
- Keep each step short enough that a non-technical WordPress user can follow it
  without help.

This is a macro: keep it as a template an agent sends as-is or lightly edits, not
a one-off reply.