I tried to reproduce this issue here on meta and I am able to reproduce it. I think it’s rate limiting issue. When I click the like 3-4 time in less that 30 seconds I get rate limiting error saying I have to wait for 30 seconds to perform this action again. I repeated this 2 times. After that I got this same error.
I think that’s due to discourse thinks you are a bot and trying to do something wrong.