normally dc convergence have following reasons:
1. models have discontinuity ,, some negative resistance in characterstics
2. simulator convergence algortihms...
3. some time design faults as well
as your simulator is giving error for convergence
i havent used this simulator but general idea:
1. try to increase accuracy levels
2. use gmin as directed by simulator command
3. try to skip dc and go directly to transient
4. if possible try to use .nodeset/.ic statements to help in convergence