Permalinks using just %postname% and 404s.

Hi all,

I’ve changed my permalink structure to Custom -> /%postname% (I know there are suggestions against this, but I’d still like to use just /%postname% or possibly /%category%/%postname%.

However, when accessing links to my site that reside on another site, they show up as 404s. I’ve tried setting up redirects by adding the following line to my .htaccess file without any luck(of course the one below is just an example):

redirect 301 /old/old.htm https://www.you.com/new.htm

I don’t mind creating redirects for all the pages, but am at a loss as to how to get this to actually work. I am I doing something wrong? Any help would be greatly appreciated.