Which are you using (Steam, Epic, or Rockstar)?
Ultimate Guide to GTA 5 DLC Packs: How to Fix Missing 'mpsum' Files update x64 dlcpacks mpsum dlcrpf download free
GTA V receives periodic updates from Rockstar, which often break existing mods. Each new title update (e.g., 1.0.3274.0, the Contract DLC, etc.) modifies the update\x64\dlcpacks structure. If you do not update your custom DLC packs accordingly, you will encounter: Which are you using (Steam, Epic, or Rockstar)
Use OpenIV’s “ASI Manager” to ensure OpenIV.asi is installed. Then launch the game. If it loads, your update was successful. Which are you using (Steam
x64
The path update/x64/dlcpacks/mpsum/dlc.rpf refers to a specific data file within the Grand Theft Auto V (GTA V)