Error code 55 appears when Steam cannot complete an installation or update, and in Valve's status list code 55 means RemoteCallFailed, a remote or inter-process call that failed. In practice it is most often reported alongside antivirus conflicts and a Steam service that failed to load, so the fix starts with security software and the Steam service itself.
The fix, in order
Restart Steam completely, using Steam, Exit, then reopen it, and try the install or update again.
Pause antivirus real-time protection briefly and retry. If the install works, add the whole Steam folder to the antivirus exclusions and turn protection back on.
Reinstall the Steam service. Close Steam, open an administrator Command Prompt, and run "C:\Program Files (x86)\Steam\bin\SteamService.exe" /Install, then restart Steam.
Verify the integrity of game files for the affected game. In the Library, right-click the game, open Properties, then Installed Files, and click Verify integrity of game files.
Clear the download cache under Settings, Downloads, then sign back in and retry.
Run Steam as administrator. Right-click the Steam shortcut, choose Run as administrator, and try the install again.
Reinstall the Steam client if the error persists, keeping the steamapps folder so the games are not downloaded again.
Do not leave antivirus protection off. Pause it only long enough to test, then turn it back on and add an exclusion for the Steam folder instead.
If it still happens
If the error only appears for one game, delete that game's app manifest from the steamapps folder while Steam is closed, then reopen Steam and install the game again. If it appears for every install, the antivirus or the Steam service is the cause, so focus on those two steps.
Common questions
What does remote call failed mean? It means a request Steam sent to another process or service did not complete. The usual reason is that security software blocked it or the Steam service itself did not start.
Is error 55 the same as error 53? No. Error 53 is about Steam being too busy or a request being blocked, while error 55 is a failed internal call, most often tied to antivirus interference or the Steam service.