Haha you knew what I was going to ask (how to install a Nightly) without me having to ask
I keep a vanilla archive of OpenXcom just for mods or for a clean start in case something horribly goes wrong.
I re-read your install instructions:
1.Rename your Data/SoldierName folder to something else.
2.Backup your original data, just in case. This mod will modify a lot of maps etc.
3.If you already have previous Piratez version, delete resources/pirates to get rid of any no longer used stuff
4.Dump the contents of the archive into the Data folder.
5.Enable Piratez, Piratez_Factions, Piratez_Planet and Piratez_lang .rul files (the last file contains all language data, ALL are required).
6.Compatible with Luke83's Extra Ufos:
https://openxcom.org/forum/index.php?topic=2007.msg19079#msg19079 (although this makes the challenge easier due to better access to some rare ship components).
7. There is an alternate paperdoll for mask-less Smokey armor available in Piratez Alternate Armor folder. Just write it over same files in the Piratez folder if you want it.
I actually don't see anywhere where it says to download a certain nightly. Since this is just text and you can't hear my tone please don't think I'm getting bitchy or snappy. I just wanted to clarify that I don't see where it said to install a certain nightly and that was where I got astray.
EDIT: Ah wait the culprit is your piratez mod page on
https://www.openxcom.com/mod/piratez doesn't list the nightly requirement. It's probably best to update that page then. I see it now on your piratez forum page.