I have made several versions from one original font, renaming each version, and I have installed them with no problem. On my latest version, when I try to install it, I get a message saying a font - a previous version with a different name - is already installed and do I want to replace it. I don’t want to replace that one. I have tried renaming the new version, but nothing changes when I try to install it.
There are two names that need to be changed — the Font Name and the Truetype font file name. Check that you have done both. Use the Autonaming wizard to rename the font, and save as to save the TTF font file.
If all else fails, reboot.