Follow these solutions in order, as they are arranged from easiest/most likely to more complex.
The failure to load a DLL can be attributed to three primary categories: Path Resolution Failures, Dependency Chain Failures, and External Interference.
Windows updates have a history of breaking Rainmeter. This is usually because an update replaced or removed a shared library.
Sometimes the installation itself is corrupt. Not the DLLs, but the registry entries or configuration files.