We designed a PCB with stm32f030c8t6. We soldered the PCB and tried to upload the code. Power has gone to the stm32f030c8t6 successfully but when we arranged a pin as a gpio output it wasn't high.

 

You tried to upload the code without success or you are uploaded code successfully?
And withot schematics and code is very hard to tell what is wrong with your design (if it is wrong).

 

You need to show the connections from the PC to the board and tell us what platform you are using to flash the MCU.

 

There is no connection error because our computer sees the microcontroller. We are using cudeid, c language

 

We used jtag connection with st-link

 

We upload the code successfully but we couldn't read the voltage

 

You tried to upload the code without success or you are uploaded code successfully?
And withot schematics and code is very hard to tell what is wrong with your design (if it is wrong).

We upload the code successfully but we couldn't read the voltage

 

We upload the code successfully but we couldn't read the voltage

If the IDE programmed the MCU with no errors then your next step is to debug your code.
Start off by doing the simplest operation possible such as flash an LED.
Do you know how to run using debug feature?
Have you configured the system clock properly?