I have two aquacultured that have never figured it out. It does happen. Pointing an isolated spotlight in a dark tank for several hours at the rbta will also sometimes work, but the strainer is one of the only methods that also works.
The anemone shrinks down almost closes at night time in the rocks and the clown will go and sleep right in front of it but during the day when the nem is out and all bubbled up the clown wants nothing to do with it.
You have a couple of things going on here - first your snowflakes are captive raised and have no natural symbiotic behavior that they became accustomed to at a young age, and second, that your rbta is not a natural host.
They may decide to go into the anemone, they may not. In the wild they locate host anemones by smell almost the moment they meta from larvae (because otherwise they are quickly eaten). If they grow up without a natural host in a breeder's tank they may never develop a strong anemone symbiotic link.
As stated above clowns usually find a spot or host something else that makes them happy, here is where at night switch out that coral for a nem and you can usually nudge them to host. I had a pair that hosted a Hammer and this worked very well.
Did they find a host in the anemone? I waited over a year before mine suddenly showed interest. Small acclimation box/vented tray with both inside will cause them to find the anemone real quick. Worked great for the pair I have now, also a captive pair and RBTA
i took a piece of plastic florescent bulb protector. (any plastic hollow tube ) put 1 end close to the anemone (like a half inch above it. then put the fish in the other end. he should swim down to the anemone. if he doesn't then scoop some water out of the tank and flush him down to the anemone. its worked everytime.