The original text of the Bidding Law reads: If the cover of the bidding document is not stamped with the official seal of the applicant and the seal of the legal representative, or the signature is incomplete, it will be deemed invalid.
Please note that there is a word "he" in the middle, so it is understood that there is no official seal and no legal representative's seal or signature, which is considered invalid; If there is one of the two, it cannot be used as the basis for abolishing the bid. This understanding is recognized and explained in the understanding documents of provincial bidding laws or local bidding regulations.
However, comparing with your description, we can find that the tender documents actually changed the original intention of this clause, and it became an indispensable official seal. Now that the tender documents have been issued, no bidder objected to this before the bid opening, and the tender documents will naturally prevail in the bid opening stage. I guess that's why your bid documents were rejected when the bid was opened, and neither the regulatory authorities nor the notary raised any objection. So, if this passage is the original text of the tender document, then you have to accept the result.
I suggest that you can study this clause in the Bidding Law and learn a lesson in the next bidding. If there is such a provision, you will raise an objection on the grounds of law, and let the tenderer change the requirements of the bidding documents according to the definition of law.