Hello,
Ukraine’s country code is 380 and cell phone numbers are 9 digit. This is what you have above so it seems you are using the correct dialing sequence. You could also try replacing the plus sign with 011 although both + and 011 should work.
Have you also tried calling this number? If calls work and text do not I would call the Canadian wireless provider to inquire about this issue. If neither works either your current plan doesn’t allow international access or there’s a problem with the Ukrainian phone.
If you want I can try calling this number to see if it works from my end.