Normally (game default) you should be offered a VIIC in flotilla 1 by now, but Sub Commander changes the dates for flotillas and which subs becomes available when and where.
So the only ways you can get a VIIC at this time are:
1. To load SH3 while you're in port after selecting 'Roll back SH3' in Sub Commander' and select the VIIC (and then exit and start using SubCom again if you wish).
2. Read up on
www.uboat.net to check where and when the different types became available and change flotilla accordingly while using SubCom
3. Wait until one of the SubCom devs answers your question :P