# VMTK library is not found and extensions are imcompatibe with slicer (MAC and Win, 4.13.0 built 2021-08-11 )

**URL:** <https://discourse.slicer.org/t/vmtk-library-is-not-found-and-extensions-are-imcompatibe-with-slicer-mac-and-win-4-13-0-built-2021-08-11/19166>\
**Category:** Support\
**Created:** [August 12, 2021, 8:58am UTC](https://discourse.slicer.org/t/vmtk-library-is-not-found-and-extensions-are-imcompatibe-with-slicer-mac-and-win-4-13-0-built-2021-08-11/19166 "2021-08-12T08:58:39Z")\
**Posts on this page:** 1\
**Showing post:** 2

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**Author:** ![jamesobutler](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/jamesobutler/32/7511_2.png) [@jamesobutler](https://discourse.slicer.org/u/jamesobutler)\
**Post date:** [August 12, 2021, 11:24am UTC](https://discourse.slicer.org/t/vmtk-library-is-not-found-and-extensions-are-imcompatibe-with-slicer-mac-and-win-4-13-0-built-2021-08-11/19166/2 "2021-08-12T11:24:02Z")

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That was an issue with yesterday’s Slicer version. Try again with today’s version.

See the following for more details

> [@Unable to install extension - "Incompatible with Slicer r30110"](https://discourse.slicer.org/t/unable-to-install-extension-incompatible-with-slicer-r30110/19158/2):
>
> Thanks for the report, it is a side effect of [Upcoming downtime for download.slicer.org and extension manager due to package server transition - #3 by jcfr](https://discourse.slicer.org/t/upcoming-downtime-for-download-slicer-org-and-extension-manager-due-to-package-server-transition/17444/3), issue has been identified earlier today and I am currently working on this. For reference, this is now tracked in [Installed extensions are not loaded · Issue #5786 · Slicer/Slicer · GitHub](https://github.com/Slicer/Slicer/issues/5786)

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_[View the full topic](https://discourse.slicer.org/t/vmtk-library-is-not-found-and-extensions-are-imcompatibe-with-slicer-mac-and-win-4-13-0-built-2021-08-11/19166)._