BAsh commonds are not accepted in terminal with mac book pro mid 2012 with SSD and mac os Catalina

I recently replaced the HDD with SSD in my mac book pro mid 2012 to install the MRtrix3.
while trying to run the installation of MRtrix3, bash is not taking any commands and i am failing to install MRtrix at repeated attempts.
can any one find a solution for this.
where as i can install the MRtrix on my mac air with out any difficulty

Can you provide a bit more context for us to figure this out? At what stage of the installation is this happening? Maybe a screenshot of the terminal would help?