https://www.epo.org/en/service-support/faq/searching-patents/open-patent-services/search-queries-tips-and-tricks/i-keep

I keep getting an error message from OPS. What does it mean?

There are several situations when the OPS system responds with an error message. Often the reason is web service unavailability, lack of server resources to process the request, incorrect request format or ambiguity.

A list of the most frequent error messages can be found in the Open Patent Services v.2 documentation.