Hey @Joebar0212 welcome to the Nextcloud community 
You posted your request in the support category. Unfortunately you ignored the template and a lot of information to help you is missing. Please edit your original post and add all required details like Nextcloud version, webserver type and version, os version, related log file content. Use the support template .
Without additional information the community members cannot help you.
However looking at the command you’ve tried sudo occ config:system:get trusted-domains you’ll not be able to `set` your trusted domains with that… prefer something like this;
sudo -u www-data occ config:system:set trusted_domains 0 --value="cloud.yourdomain.tld"
Note how you assign a separate ID number (iterating values 0, 1, 2…) for each trusted domain.
Set multiple trusted domains (iterating values 0, 1, 2…):
sudo -u www-data occ config:system:set trusted_domains 0 --value="cloud.yourdomain.tld"
sudo -u www-data occ config:system:set trusted_domains 1 --value="cloud.yourseconddomain.tld"
sudo -u www-data occ config:system:set trusted_domains 2 --value="cloud.yourotherdomain.tld"