Contact Form not receiving emails when not set to site offline - Joomla! Forum - community, help and support

hello,

i new in joomla.
i have contact form , works last november.
but days after did extension update of "jch optimized" , "sourcererslab", contact form isn't working.
there inconsistency, sends not.

i test extension update first in test environment site, , no problem occurred.
but when execute update on production site, contact form doesn't send email.
it difficult duplicate error in test environment, , didn't same error.

i checked global configuration, mail settings set correctly, , have tried php mail, sendmail , smtp, , working fine.

after read article, stated, "sometimes jch optimize extension' stuff breaks without noticing right away, , possible issues can contact forms not working."
reference link : https://[spam]/cykpvf
i tried disable minify js , css area in extension of jch optimized, still didn't work.
also tried disable whole plugin , delete cache, didn't help.

other things noticed when turn offline:
- contact form working well. received emails on messages sent during site offline.
- there success , error message displayed.

but when returned online:
- contact form doesn't work again.
- , there no error message when send message in contact form, success message.

i not sure if there error has not been caught or what?

can me?

thank you.

/** joomla version: 3.6.4 **/

regards,
raine

the reference link became spam:
kindly remove spaces on link. thanks.

https:// joomlaseo . com / seo-extensions / jch-optimize