Hi gasparraco, Welcome to EasyEDA. Can you make a copy of your circuit public so that we can have a look at it to see what the problem might be? In the meantime, you may find some hints in our spice book: <https://easyeda.com/Doc/Simulation-eBook/Introduction-to-using-a-simulator.htm#Avoidingcommonmistakes> :)

This is probably because you have a syntax error in the circuit. For example if you have a source with an argument (a value) defined by a parameter, for example to set the frequency of a sine souce: SINE(0 1 {freq}) but in the parameter definition itself you have made a typo such as: `.param frequency=1k` then when you run the sim you will see the "Connecting to server: Waiting" whirly for a while and then nothing else will happen and your Simulation results window may also be blank or show the results of the last successful simulation. The same thing can happen if you have forgotten to set the `.param frequency=1k` statement to be a spice directive and have left it as a text comment: ~~~~ To set a spice directive as inactive text (blue non-italic font): a) Select a spice directive; b) Do: Properties > Text Attributes > Text type > comment To set a spice directive as an active spice directive (black italic font): a) Select a spice directive; b) Do: Properties > Text Attributes > Text type > spice ~~~~ a illustrated in: easyeda.com/editor#id=db5mgyQ8q|wuohbtLFX|OKVvtr1Ay or if you have forgotten to create a parameter definition at all. The error reporting for these kinds of problems needs to be improved but basically when this happens: carefully check the syntax and that the spelling of any parameters used in spice directives, expressions and statements are the same wherever they are used.

Sorry that should have said: as illustrated in: <easyeda.com/editor#id=db5mgyQ8q|wuohbtLFX|OKVvtr1Ay> :)

Doh! as illustrated in: <https://easyeda.com/editor#id=db5mgyQ8q|wuohbtLFX|OKVvtr1Ay>