Quick answers for duplicate highlighting.

Select one continuous range, then choose Refresh selection in the sidebar. Merged cells, protected ranges, and unsupported multi-range selections may need adjustment.

Preview reads the selected values locally and may be unavailable for very large selections within Apps Script time limits. Applying can still work because the native rule does not require reading every selected cell.

Turn on Trim spaces and, if appropriate, Ignore case. Numbers, text, booleans, dates, blanks, and error values can remain type-distinct even when their display looks similar.

Check which Clear you used. The sidebar's Clear this selection only removes rules inside your selected range, while Extensions › Clear all highlights on active sheet covers the whole sheet. Either way, Clear removes only rules Duplicate Highlighter can verify it owns; if a rule was manually edited or copied, remove it through Format › Conditional formatting.

Undo last highlight reverses the most recent apply and stays available after you reopen the sidebar, as long as that rule group is still intact and verifiable. It is conservative: it never guesses and will not overwrite unrelated formatting. It is not offered for Clear, and it is not in the Extensions menu.

Make sure the Google account that authorized the add-on is still signed in, then use Refresh access. If the issue continues, disconnect and reconnect the account from the sidebar.

Return to the sidebar and choose Refresh access. Stripe checkout does not grant Pro by redirect alone; the signed billing webhook must confirm the active subscription.