Horned frog breeding, help needed

Hi all, I have been trying to breed my pacman for some months now, and for some reason my females keep laying eggs but the males don't go into amplexus. These are all almost 2 years old. All 4 females are cranwelli, and I have 2 cranwelli males and 2 ornate males.
Males always call when in the rain chamber.

I tried the following combination in the rain chamber:

1 male 1 female no cooling, got eggs no amplexus.
3 males 2 females after 3 weeks cooling, no eggs no amplexus. Removed 1 female and 1 male and still nothing.
2 males 1 females no cooling again, got eggs no amplexus.
2 females 1 male no cooling, got eggs no amplexus, added a ornate male and got eggs no amplexus.
1 male 1 female after 5 weeks of cooling, 2 days warming up, 1 meal then to rain chamber, she just laid eggs tonight with no amplexus. I just added 1 ornate and another cranwelli male to the rain chamber.

Is there a way to milk the males for sperm like you can do with some fish?

Any help will be appreciated.:confusd: