Because the official remaster only includes geometry utilized during the linear story mode, exclusive standalone maps from the original 2009 Spec Ops (such as the bridge map "Suspension" or the oil rig fallback "Wreckage" ) do not exist natively in the files. To solve this, developers use two primary workarounds:
Importing level environments from related game engines. For instance, the famous mission "Hidden" was restored by porting the engine data from the "All Ghillied Up" mission found in Modern Warfare Remastered (MWR). Supported Operations Matrix h2 mod spec ops
The mod repurposes original Halo 2 maps for spec ops objectives: h2 mod spec ops
In the launcher, check the following:
Ensure your copy of MW2CR is cleanly installed without existing file corruptions. h2 mod spec ops