Python 3.9 has few major changes and might not be supported. So maybe trying python version 3.6 might have luck. This is likely the issue in your case. There are several breaking changes with python 3.9/3.8.
conda create --name simlord_env python=3.6.5
Then activate the environment.
conda activate simlord_env
Now install simlord using the command;
conda install -c bioconda simlord
This way simlord command will be available whenever simlord_env is active in your terminal.