1906a656_uide_to_Small_Batch_Composting__POSSIBLE_CAUSE
[SYMPTOM] Compost is not heating up [POSSIBLE SOLUTION] If you add your material slowly over time, you may need to live with cold composting. [POSSIBLE CAUSE] 
Small compost batches are harder to heat so more care is needed. Be sure you prepare and add material all at one time to create a single batch.
How to Compost: Guide to Small Batch Composting
POSSIBLE CAUSE