Welcome to the community! and thanks for trying out SuiteCRM 8.
We’ve seen this error happening when there is some misconfiguration in mod_rewrite.
Could you double check if you have mod_rewrite active?
Also please check if your vhost configuration is set to allow overrides. Adding an example next:
Allow from All
I think the issue you are having is the same as the following, you could find more information here:
I am quite comfortable with computers, but IIS is not part of the comfort zone.
I see no rules in the URL rewrite menu. Should there be one, and what should be added?
As for the vhost configuration: where to set this.
Sorry for being so ignorant.