how do you send a fax to square up?

[fax]

their fax keeps say fax  has failed, using #877-805-2214

[VanKalkerFarms]

You can contact support by phone or email. Perhaps one of those ways would be easier than faxing. https://squareup.com/us/en/square-support

If you've already been in contact with someone from Square about an issue, contact them in whatever way they've asked besides sending a fax.