This can happen with mismatch in versions between Elasticsearch-PHP and Elasticsearch. Documented in the Elasticsearch-php library github page explains the compatibilites between them: https://github.com/elastic/elasticsearch-php?tab=readme-ov-file#compatibility

The Elasticsearch client is compatible with currently maintained PHP versions.

Language clients are forward compatible; meaning that clients support communicating with greater or equal minor versions of Elasticsearch without breaking. It does not mean that the client automatically supports new features of newer Elasticsearch versions; it is only possible after a release of a new client version. For example, a 8.12 client version won't automatically support the new features of the 8.13 version of Elasticsearch, the 8.13 client version is required for that. Elasticsearch language clients are only backwards compatible with default distributions and without guarantees made.