ERROR: Input file must have IDF, IMF, or epJSON extension.
Initializing workflow. Processing OpenStudio Measures. Translating the OpenStudio Model to EnergyPlus. Processing EnergyPlus Measures. Starting Simulation. ERROR: Input file must have IDF, IMF, or epJSON extension. Failed.
@Abhishek are you using the OpenStudio application to run this simulation? Are you applying any OpenStudio Measures or EnergyPlus Measures?
If you are using the OpenStudio Application try export to IDF in the file menu and see if that works. It will indicate if there is an issue in forward translation from OSM IDF. Although even if this works, it would not reflect application of OpenStudio or EnergyPlus measures. But this will help see if issue is in base file or is related to changes made by measure.