# Unknown format error

**URL:** <https://community.tetra4d.com/t/unknown-format-error/263>\
**Category:** Tetra4D Reviewer\
**Created:** [May 19, 2020, 7:52pm UTC](https://community.tetra4d.com/t/unknown-format-error/263 "2020-05-19T19:52:02Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![JFRA](https://avatars.discourse-cdn.com/v4/letter/j/e68b1a/32.png) [@JFRA](https://community.tetra4d.com/u/JFRA)\
**Post date:** [May 19, 2020, 7:52pm UTC](https://community.tetra4d.com/t/unknown-format-error/263/1 "2020-05-19T19:52:02Z")

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I am trying to load a .prt file into Tetra4D Reviewer to export as a 3D PDF. I have done this in the past. But for some reason, the current file is throwing this warning. Not sure where to begin with troubleshooting my file as it is certainly a file Tetra should be able to read.

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**Author:** ![Tetra4DSupport](https://sea1.discourse-cdn.com/flex019/user_avatar/community.tetra4d.com/tetra4dsupport/32/188_2.png) [@Tetra4DSupport](https://community.tetra4d.com/u/Tetra4DSupport)\
**Post date:** [July 6, 2020, 3:44pm UTC](https://community.tetra4d.com/t/unknown-format-error/263/2 "2020-07-06T15:44:07Z")

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Hi,

Your file looks to be a NX file, and it could be a version issue. Please contact us at the support, through the Customer Portal or via an email. e will review with you your version, and the version of your NX file.

Thanks,

The Support Team