Welcome to the Atlassian developer community @AdamKrauss,
Issue types are also constrained by the project. In other words, project 10015 might not have issue type 10188. It might help to [get the metadata for creating an issue]( Get create issue metadata) using GET /rest/api/3/issue/createmeta. You can narrow the project scope with the projectIds parameter. The result returns an array of projects (even if 1 when you send ?projectIds=10015), each with an array of valid issueTypes. Can you confirm that 10188 is in $.projects[*].issuetypes[*].id (a little JSONPath to be clear on the JSON navigation)?