Some bad news, buses are replacing trains on all lines in and out of Wellington on the 27th and 28th of April. Kiwirail must hate us.
The only things I can see are buses all day Anzac Day, and for the Wairarapa in the weekend.
EDIT - Found it. While the info is not in their notifications for next 7 days (yet), it's on their calendar of upcoming bus replacements https://www.metlink.org.nz/news-and-updates/buses-replacing-trains/kapiti-line/