Years ago I bought a collection of OPTIfonts which I still use on occasion. InDesign today is not letting me use OPTI Calculator, a digital alarm clock face. It either won't recognize it (even though it shows up in the list of fonts I activated, or somehow is blocking from use. WTF?
I don't know if this is the same Opti font or not...
If you installed it while ID was running, perhaps a simple exit and restart of ID will cure the issue.
ID is notorious for not liking fonts that are (or at least ot it are) corrupted. If your font previously worked, I would unintall it, reboot to clean out the font cache memory, reinstall it and see if it is now working. Then again, usually ID won't even list such fonts.
If this is the first go with this font, and depending upon the download, it is possible it was always corrupt and just now showing its problem. If the above font is the same as yours, let me know via a PM and I can get you a copy.
Thanks. A reboot worked.