When you run the Reqtificator, it should ask you to locate your plugins.txt file.
As I only use mod organizer, I will only comment about mod organizer problems. You will save yourself a lot of trouble in the future.
Before we begin, please use mod organizer. Most of the time reading directions is more than enough to successfully complete the install, but here we are. Requiem itself is more involved than the creation club style of modding and newer members of the modding community will often have difficulty installing it. Check them out the modlist authors have carefully curated a functional load order to save you the trouble. Several popular ones include Noir, Total Skyrim Overhaul, and Serenity, each much different than the last.
Wabbajack contains several mod lists containing Requiem for SSE and the converted files are the same ones discussed earlier, although you will not have to manually download them if you use the automated installation option with Nexus premium.
The best way to find these available patches are visiting the LL website and there are links to converted mods and file hosting sites, searching the SSE Nexus for “requiem”, and searching the Discord under “Mod Releases.” VI. If using any of these, please download the original LE file to show your support if applicable.
Popular mods including 3tweaks and Vigilant patch are available already converted on the file hosting sites, while other mods like Fozar’s Dragonborn and AzTweaks are officially out for SSE on the Nexus.
However, some Requiem-SSE specific patches and mods are also available on the Nexus, despite not having an SSE version of Requiem on the Nexus. Many mods have been converted and are available from those file hosting sites I mentioned earlier. See this reddit post for further information: V. They are not affiliated with the original authors. They are personal files that users have converted to share with those who would like to use them too. These releases are not official, and they are not uploaded on the Nexus. If you are to use these, please also download the original LE versions of the mods to show the authors support. Most people go this route and download it from here. There is also a file containing Requiem’s converted files to SSE, along with links to several people’s personal dropboxes/google files with converted Requiem patches on the LL Requiem SSE page. With some time, you can convert Requiem to SSE yourself. There is a popular guide on Lover’s Lab (LL), a 3rd party site known for hosting explicit 18+ Skyrim mods. People have taken to expediting Requiem’s port to SSE by implementing it themselves. Historically, things have not progressed very quickly, so do not expect 5.0 to be released only a couple weeks later. The Requiem team does this as a hobby, not a job. The official 4.0 and 4.0.1 versions have just been released as of July 2020. Requiem 4.x is stated to be the last version of Requiem for LE, after which 5.0 will be a direct port of 4.x and be an SSE exclusive. Why am I posting this? There are too many people asking the same questions both here and, on the Discord, and I felt like we should have a place with consolidated information that people could easily find. With better graphics and a more stable game, there is no questioning SSE is the way to go. With SSE having become the primary modded game these days, people have been anxiously awaiting Special Edition support from Requiem.
Skyrim Special Edition has been discussed for years now.