"Můj manžel zase spí."

Translation: My husband is sleeping again.

[Samaelch]

Why can't I use "My husband sleeps again"?

[kacenka9]

Because he, obviously, is in the process of it, right? otherwise you would not have the 'again' in there. And as such you need to have continuous tense

[Zeego1]

And why not "My husband is asleep again"?

[VladaFu]

It is not so literal - a specific verb vs. to be and an adverb. But since we have no direct Czech equivalent of asleep, I will add it. We do have vzhůru for "not asleep" in Czech and we have "spící" for "sleeping".

[Annatamoracz]

However, if your husband has had a long period of troubled, sleepless nights, but now he finally is sleeping normally again, I think one would indeed say "My husband sleeps again". (I think - non-native speaker though.)

[Eric36363]

Bud' pracuje příliš mnoho, nebo je liný