I have a betta that has a ten all to himself and has for over a year, he's fine happy and healthy and has never built even one, so I wouldn't worry. All your params check out and he is eating normally, correct?
Try using live/frozen foods along with increasing the temp to around 81, that usually triggers a reproduction response which will encourage the bubbleness building. Hope this helps.
If you are trying to breed you need to introduce him to the breeding tank, which if properly setup, usually inducing them to want to start building a nest. Lacking that reaction, adding the female if he is ready and prime to breed (and most males are) will get him working on one double time. Though I have had them spawn without the nests before...
Not all males build bubblenests in their holding containers, many do, but not all. In fact of my bunch now only 2 do. This simply means they are lazy! Or that they don't find their quarters particularly... nest worthy.
I have a white roundtail. He never created a single bubblenest since I raised him from an inch size. He is now 2 inches I think. The only ones that ever create bubblenests are the marble doubletail and a cross of veiltail and crowntail.
Most likely you do not have a heater for the bowl, if a betta is not kept around 80 generally they will not blow bubblenests.
Also as a cautionary note, I am hoping you are not planning to house your male betta and female betta in the same enclosure. Because unless its exceptionally large, the male and female will not coexists safely in most cases.
I have a veil tail that built nests almost daily when he was in his (temp) 1 gallon bowl; now that he is in a 10 gallon tank - he has never built another one. He appears healthy and happy tho........(reminds me - my sis was fish sitting while he was still in the bowl and she called me all frantic cuz there are bubbles all over!?! Is he ok?!? I told her don't worry, he's just trollin for chicks!) :rofl: