I got this issue on our migration to spring boot 3.4.2 too.

I tried spring-cloud-starter-circuitbreaker-resilience4j, with no chance.

I discovered that a dependency was missing:

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-aop</artifactId>
    <version>${spring-boot.version}</version>
</dependency>

I got the hint from https://stackoverflow.com/a/61930362.

spring-boot-starter-aop was dropped in spring-cloud-openfeign-core:4.1.2.

Here is the commit who removed this dependency: https://github.com/spring-cloud/spring-cloud-openfeign/commit/6084609de0705f24ba418704769e545a0d820d70

I don't know why it was removed and what is needed from there, but adding it back makes my circuitbreaker work again.