The error says

" Problem with endogenous capacity addition calculations. This may indicate the Demand is growing too fast. Alternatively, check there is sufficient capacity.

Branch: Transformation\Electricity generation\Processes\Existing coal steam

Scenario: Reference

Year:2011"

The "Exogenous capacity" for "Existing coal steam" in scenario Reference are set to Step(2020;500;2030;0)

and the Endogenous capacity for "New coal steam" and "New oil combustion" are set to 500 and 300.

This error is very often (not always) caused by electricity demand that is growing too quickly/too large in the first place. Try following the recommendation that I described in this post, disabling Transformation & Resources until you're certain that your demand calculations are correct.

Best,

Taylor