HPS ballast problem?

Hi All, I have been looking extensively online for an answer to my problem but have not been successful.
Here is the situation: I have a 400w HPS setup with digital ballast. My old original bulb still works fine (no flickering, half decent light output), but four different replacement bulbs from 2 different manufacturers will not work with the same gear.I keep going back to using my old bulb because it still works.
Why would new bulbs not work but the one old one starts up perfectly each time?
Is this a sign of ballast failure?

Thanks
Ian

What ballast and bulbs? Are they both hps bulbs

Yes, all bulbs are 400W HPS, two of the new bulbs were Apollo and 2 were iPower, so not premium bulbs but neither was the original generic hps bulb that came with the set. The ballast itself was from LEDwholesaler but does not show a brand or manufacturer.

ianinbc said:

Yes, all bulbs are 400W HPS, two of the new bulbs were Apollo and 2 were iPower, so not premium bulbs but neither was the original generic hps bulb that came with the set. The ballast itself was from LEDwholesaler but does not show a brand or manufacturer.

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Contact apollo and ipower and explain your deal...