Signal Tap does not support the OpenCore Plus Hardware Evaluation feature

Without JTAG, when Nios boots, it will look for code at the reset vector you set in the Nios parameter settings.

You're saying your processor isn't connected to anything? You have to have the instruction and data masters connected somewhere.

Try using the Lite edition of Quartus instead of Standard unless you have a license for Standard edition. If you don't, have you gone beyond the 30 day trial period for Standard?