Certifications done by factory, but product has my brand name – Temu won't accept it. Do I have to redo all certs?

To answer your second question: Yes, if you want your name as manufacturer on the product, you generally need certificates under your name for each product. That's just the cost of private labeling.
Some labs will do a "family model" certification where one test report covers multiple similar products, but the manufacturer/applicant still has to be consistent. Talk to a testing lab about bulk or family certification – it's cheaper than doing each product individually.

This is the key comment
DO NOT edit certificates.
I had a client who did exactly that – found someone online to edit the PDF, changed the manufacturer name, uploaded it, got approved, sold for two months. Then Temu ran a check, found the certificate number didn't match what the testing lab had on file, and fined them over $7,000. They banned the store and kept the money.
Here's how it works: Temu (and Amazon, and others) can take your certificate number and check it directly with the testing lab's online portal. If what you uploaded doesn't match what the lab issued, you're flagged for fraud. It doesn't matter if the test results themselves are legit – the document is considered fake.
Your actual options:

1. Get a new certificate under your name. Work with the factory's testing lab or a new lab, have them re-issue the certificate with your company as the applicant/manufacturer. This costs money, but it's clean and you won't have problems later.
2. Ask the factory to do a "certificate split." Some labs will issue a separate certificate under your name based on the original test report. It's usually cheaper than full retesting. The factory has to cooperate because they're the original applicant.
3. Put the factory's name on the product. If you're OK with that, you can change the product labeling to match the factory's name and address on the certificate. But then your brand isn't on the product.

There's no magic shortcut. The system is designed to catch mismatches, and they're getting better at it.

One more thing: This isn't just a Temu problem. Amazon does the same thing. If you're selling electronics in the EU or US, they'll flag manufacturer mismatches eventually. Better to set it up clean from the start.

Workaround if you're willing: Keep the factory's name on the product as the manufacturer, but add your brand as the "brand" or "distributor." That way the label matches the certificate, but you still get brand recognition. Check if the platform allows that format.

DO NOT edit certificates.*
This should be pinned. I've seen so many sellers think "it's just a PDF, no one will check." They check. And when they check, they don't just reject the listing – they fine you and hold your funds.