Do you have languages downloaded in Translate App?
I am not sure if this help but I never had this issue since I have downloaded Polish, English and other languages.
There is also “On-Device Mode” in Settings > Translate (here you could download offline translate files).
Hi, i checked on the internet, that installing offline languages may help. It did not. But now, after installing new OS version it started to work. I think not this update helped but maybe something was cleaned up in app cache or something - it is translating from EN to PL and from PL to EN (before usually it was working PL - ENG, but not every time).