Quick tips for anyone who may encounter this error:
LogChunkDownloader: Error: Manifest parse error at …/PersistentDownloadDir/PakCache/CachedBuildManifest.txt:3
…
I wasted a day of my life trying to figure out what was wrong…
It is VERY important to keep this format for each pak line in your BuildManifest files:
NameBuffer[TAB]FinalFileLen[TAB]VersionBuffer[TAB]ChunkId[TAB]RelativeUrl
Ex: pakchunk2001-WindowsNoEditor.pak[TAB]649382806[TAB]ver001[TAB]2001[TAB]/VariantA/pakchunk2001-WindowsNoEditor.pak
[TAB] = The real TAB character (ASCII #9). Not space or any other characters!
I got this error when using VSCode to edit my BuildManifest files. With VSCode, when you press the TAB button on your keyboard, it actually adds 4 space characters instead of a real TAB character. This means that your pak list in the BuildManifest will not follow the correct structure and it will crash. You can see where it crashes in the code here: ChunkDownloader.ccp line 332.