Authenticity cannot be settled on a video call. For comics the two worries are a reprint described as an original and undisclosed restoration, and they need different questions.
What to ask them to show
The small print block inside the issue, in full and in focus. Whatever a comic's printing details are, they are stated there, and a photograph of that block can be read by somebody who knows the title.
The cover, square on and filling the frame.
The spine and the staples, close up.
Pages fanned under light, which is a request a seller can meet in seconds while live.
Asked outright: has it been restored, pressed, cleaned or had anything repaired? Each of those is a separate thing and all are disclosable.
What a refusal means
A seller who will not photograph the print block of a comic they are describing as a first printing has withheld the one page that speaks to it.
"It has never been touched" is a strong claim. Ask what it is based on — a strong claim with a vague basis should move your price.
What this page will not do
It will not tell you how to read a printing block, how to recognise restoration under light, or which printings matter. Restoration detection in particular is a specialist skill with real equipment behind it.
Get the photographs, then ask a collector of that title, or buy a graded copy.
What protects you if you get it wrong
A reprint sold as a first, or undisclosed restoration, is not as described: returnable for 7 days whatever the store's policy says, and reportable.
Ask about packing as well — humidity and a bend at the spine do more harm in this category than any forgery, and both are avoidable with board and a rigid mailer.
Questions people ask
Does a graded comic settle it?
It moves the question to the grader and the holder. Ask for photographs of the label and the case.
Is pressing the same as restoration?
They are treated differently by different people, which is exactly why you should ask about each by name.
Is a reprint worthless?
No. It is simply a different thing, and the listing has to say which it is.
More: spotting a counterfeit before you bid, Metzee's position on counterfeits, reporting a seller, questions to ask before bidding on comics.