Found the solution not long after posting this. If anyone else encounters this problem, here it is - I saved the .xlsx MS Excel 10 file as .xls Excel 97-2003 and this helped. Spss 23 opened it and all the Cyrillic was saved and readable.
Now on the next challenge! I am currently reading SPSS for Dummies
so hopefully, if have more questions for this forum, they won't be this stupid