FYI: The page with the "Senior Platform Engineer" offer[1] suggests visiting "general introduction"[2] or "general vacancy introduction" page, links it multiple times as HTTP not HTTPS and on the linked page, there's a non-working link "submit a speculative application" in the first paragraph and a list of what seems to be outdated positions with no current ones.
[1] https://jobs.solarmonkey.nl/o/senior-devops-engineer
[2] http://engineering.solarmonkey.nl/jobs/