A possibility, but not necessarily the reason, is a counterfeit/fake Sandisk SD card. Some places, particularly eBay has been a source of fake cards. Even Amazon if from a 3rd party seller and not sold by and from Amazon
Thank you. It doesn’t look like a fake card. It looks perfectly legit. I also bought it in a physical store, so the risk of it being fake should be close to zero.
You are a lifesaver! (SD card was locked)
Glad to have helped.