Glassdoor and Indeed have recently partnered up to streamline job posting. All jobs you post to Indeed will now be posted to Glassdoor as well. This works automatically for both free and premium postings. Hence, it is not possible to directly post your jobs to Glassdoor anymore.
To post your jobs on Glassdoor, make sure auto-posting to Indeed is enabled in your account.
Go to Settings > Apps and plugins > Job boards and click Manage next to Indeed to check if this is enabled.
You can find more information about the partnership in Glassdoor’s help center.