Error 404 on [server]/_search (works fine on my other instance!)

Hello guys!

I am scratching my head to understand why the same very simple query works fine on one instance (v. 7.6.0) but does not work on my other instance (v. 7.9.3) - I get 404.

curl --location --request GET 'https://(instance_address):9243/_search' \
--header 'Authorization: Basic (instance user/pass)' \
--data-raw ''

When it works (instance A):
image

When it does not (instance B):
image

Interestingly enough when I run both queries within Kibana console both queries return valid results.