Login button is broken on Linkedin. They suggest that I use another browser

Switching browser usually means that you don't have any extensions installed, no caching, no local storage, probably no malware and so on.

They suggest you to _try_ another browser and see if that's fixed. If is fixed, there is a problem on your side. If is not, there might be a problem on their side.

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TLDR: that looks like a standard/automated reply