Microsword is a hit or miss plant. I've never seen it moderately grow. It putz's along or it blankets your tank in 3 months (when you separate it, as you have done). Lighting doesn't seem to be the magic bullet, as it will grow as much under the shade of other plants as it will out in the open. I've also grown it equally well from 2wpg to over 4wpg (same tank). However, this may be the result of "sharing the load" via its runner system. What DOES appear to be very important is CO2. I haven't been able to ever grow the plant without at least 20ppm (30-50 is better).
Finally, if you bought your microsword (rather than trade), there is a very good chance that is was grown emersed, especially if it came in a small pot. In this case, all the original growth will die off. It will also take weeks for new growth to gain any momentum.
If this is the case, it is likely that your microsword will take considerable time to carpet your tank. I recommend you try another foreground plant, but do NOT remove the microsword. Let it acclimate and start spreading while you enjoy your "easier" foreground. Then, when it gets going, remove the other forground and replant your microsword. It will be well acclimated to your tank, and should spread quickly.