Likely non-regular network  If you have designed a few circuits using the TINA program, it is quite likely
that you've already encountered this error. You will not be able to run a simulation until you can find the cause
of the problem. Here are a few tips:

1. Make sure that you have a valid input and output source selected.
2. Look around your schematic for a stray piece of wire. It may be highlighted in red, and delete it.
3. Check that no two capacitors are in series, if they are, then connect a high value resistor across one.
4. If you are using a current source try shunting it with a very high value resistance say 1T.