Entry fields are missing. The entry form is blank.

Hi. I have a problem with MultiTerm. I cannot add new entries or edit exising entries. Entry fields are missing. The entry form is blank. This problem first appeared in MultiTerm 2017, right after the upgrade. But somehow it affected the previous versions as well - MultiTerm 2015 and 2011.
In MultiTerm 2017, there is no error message. In the previous versions (2015, 2011), I get a message: "LNG is missing!" when I open a termbase. Does anybody know the solution?