object reference set to an instance of an object

Question

When I create a new project or translate as single document from certain txlf files, I receive the above message and cannot proceed with translation. 
 I can successfully create a new project or translate as single document from some txlf files but I cannot with other txlf files. 
 In either case, I can open all txlf files with Wordfast Pro 5 without a problem. 
 Will you advise me what to do? 
 I am using SDL Trados Studio 2019 SR2 - 15.2.7.2849 which I believe is the latest version.

Paul Filkin · Answer

Takeshi Horii 
 This may be related to the language codes. Try changing them to be fully qualified language codes (en-US as opposed to just en for example) in the TXLF. If that does not help can you share a TXLF file that you cannot open? You can send it to pfilkin@sdl.com if that's ok.

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object reference set to an instance of an object