I don’t know the difference between a 3B and a 3B+, nor importantly, whether it’s significant. There was a problem with a speed setting, I think it applied only to a Pi 2, and I thought that had been fixed - are the cards recently bought?
I’d suggest, if you have a computer with a card reader/writer, you could download a new image and write it to the ‘faulty’ card (using Balena Etcher is the easiest and safest - Using Etcher tool to flash emonSD image to SD card, or there’s this Alternative to Etcher to write images: USBImager).
If you don’t want to try that (or if it fails) then it could be a faulty card - email the shop with your order number and refer to this thread: [email protected]