If you try installing the clip with o-rings removed, or even with outer plate removed, and it won't go on then it sounds defective. Though you're outside the Amazon return window, it might be worth a shot to contact NICHE to see if they'll warranty it. Thanks for sharing your experience at the least, so others know about the quality control issue with NICHE chains.
The DID VX428 sealed chain can be a struggle as well, but other sealed chains aren't and the RK MRU chain I just put on my Dax went on with ease. I didn't even need to pinch the plates together with pliers to compress the seals before slipping the master link clip on.
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