Do you have another pair? If so, does the left click in place properly? That will tell you if it is the Switch or the control with the issue.
If it is the Switch, then try phoning Nintendo. If you try going via email/website you need proof of purchase etc. but on the phone you may be ok - I believe Kree said he did not require anything when he sent his off?
If it is the control, you can always be a bit cheeky and buy another pair with receipt, then return the defunct pair to them. (Not that I am condoning such action, but technically it is an option)
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Glad to hear people are happy with Sonic, personally never liked the games so sadly not one for me, but appreciate it is a big deal to many a persons younger days, so glad they did it justice!