It usually takes a bit of time for a new routine to settle down, maybe just try a bit longer and see how things go.
It may also be that he needs more physical exercise to tire his body before he can sleep, I do remember a phase like that before naps and for a long time we had lots of physical activity between dinner and BT because he needed to get rid of his energy then too - although sounds like yours is settling very well at night
If he misses a nap completely I would suggest an early BT, maybe 5.30 rather than 6.30pm.