many dupes?

Yeah, they can. Try to use different devices if available.

somebody mentioned he used diff numbers but same address, device and card, but no issue though.

yeah.. got it before.
rule of thumb, one account to one phone only.

Have you fixed the problem? My second account also same

you may always cancel anytime but seller has the rights to accept or reject.
shopee system detected the same phone has been used on many account so does not allow to use that code.
These codes are usually like birthday codes and/or inactive user (long time no purchase made) codes.
You may not use those codes on the account however u may still use other general codes.