The ban came due to the ITC ruling that Apple infringed a patent belonging to Masimo regarding technology to determine blood oxygen saturation. Despite Apple’s attempts to appeal the decision, the ITC rejected the appeal, leaving the US President’s veto as the last hope for intervention; This hope is extinguished.
The ban only applies to Apple stores, so customers can still buy the Watch Series 9 or Watch Ultra 2 at stores like Best Buy and Target. With limited options, Apple may consider changing the blood oxygen sensor software or reaching an agreement with Masimo to resolve this unprecedented issue.
Source: Ferra

I am a professional journalist and content creator with extensive experience writing for news websites. I currently work as an author at Gadget Onus, where I specialize in covering hot news topics. My written pieces have been published on some of the biggest media outlets around the world, including The Guardian and BBC News.