Well I downloaded the owners manual which has an electrical diagram in it but it wasn't very useful. It's not a full schematic so you can't determine if there's anything common to the two circuits other than there relays and terminals seem to be in the same corner of the motherboard. Being in such close proximity, their two relays might share a common component just ahead of them but there's no way to know based on that diagram. How hard and expensive would it be to find one of those relays and solder it onto your mobo in place of one of the existing ones?
Always do the easy things first. Have you checked continuity on the wires going between the mobo and the two non-working components? I know it doesn't seem likely that both would have a faulty lead wire but you need to eliminate that - this is assuming you re-used the lead wires from the original components. If both lead wires came new with the replacement components then it's quite unlikely they were both defective.
Beyond that, I think you might have to look at the mobo. If you're lucky, you'll be able to spot a burnt component like a capacitor or something that you could replace on the mobo. If not, there's probably a good chance you'll have to replace the mobo. From what I understand, 10 years is when you might start to expect to have to replace a mobo and at 20 years, it doesn't owe you anything and it would not be surprising if something on the board has failed. It's probably something common to just those two circuits but it could be the same thing, (e.g. the relay) on both circuits or maybe different things on each of the circuits. I know that doesn't help much. I tried to find a better schematic for the board but couldn't.
If it does turn out to be the mobo and you don't want to spend the money on it, then you might consider powering the circ pump independently bypassing the mobo and either letting it run 24/7 if that's what it used to do or run off a programmable duty cycle timer. You could do the same thing with the ozonator. I mean, those two things don't HAVE to be controlled from the mobo do they? If that part of the mobo has failed then don't use it and power those things another way. I think I saw a decent programmable duty cycle timer with 120V output that could control at least two devices independently on Amazon for around $20 USD. You could also look on eBay and Aliexpress for one as well. I think I'd much rather do that than fork out $500+ USD for a new mobo.
Good luck with it.
