# Upgrade error from 2.16.3 to 3 **URL:** \ **Category:** Mautic 3 - Install/Upgrade Support\ **Created:** [August 19, 2020, 12:25pm UTC](https://forum.mautic.org/t/upgrade-error-from-2-16-3-to-3/15714 "2020-08-19T12:25:44Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![martinstrom](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.mautic.org/martinstrom/32/433_2.png) [@martinstrom](https://forum.mautic.org/u/martinstrom)\ **Post date:** [August 19, 2020, 12:25pm UTC](https://forum.mautic.org/t/upgrade-error-from-2-16-3-to-3/15714/1 "2020-08-19T12:25:44Z")
**Your software** My Mautic version is: 2.16.3 My PHP version is: 7.2.33 **Your problem** My problem is: After running the v3 upgrade script the second time my installation fails… These errors are showing in the log: Command output: // Clearing the cache for the prod environment with debug true In FileLoader.php line 168: Notice: Undefined variable: container in /app/config/config.php (which is loaded i n resource “/app/config/config.php”). In config.php line 12: Notice: Undefined variable: container cache:clear [–no-warmup] [–no-optional-warmers] [-h|–help] [-q|–quiet] [-v|vv|vvv|–verbose] [-V|–version] [–ansi] [–no-ansi] [-n|–no-interaction] [-e|–env ENV] [–no-debug] [–] ERR\_BUILD\_M3\_CACHE: Failed to build cache for Mautic 3. All your data has been successfully migrated to Mautic 3, but this error very likely needs to be fixed before you can start using Mautic 3. Command output: // Clearing the cache for the prod environment with debug true In FileLoader.php line 168: Notice: Undefined variable: container in /app/config/config.php (which is loaded i n resource “/app/config/config.php”). In config.php line 12: Notice: Undefined variable: container cache:clear [–no-warmup] [–no-optional-warmers] [-h|–help] [-q|–quiet] [-v|vv|vvv|–verbose] [-V|–version] [–ansi] [–no-ansi] [-n|–no-interaction] [-e|–env ENV] [–no-debug] [–] ---
**Author:** ![silavapi](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.mautic.org/silavapi/32/7424_2.png) [@silavapi](https://forum.mautic.org/u/silavapi)\ **Post date:** [August 19, 2020, 5:08pm UTC](https://forum.mautic.org/t/upgrade-error-from-2-16-3-to-3/15714/2 "2020-08-19T17:08:44Z")
Hi there, does your Mautic instance load? If there are errors, try clearing out /var/cache and then reload. ---
**Author:** ![martinstrom](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.mautic.org/martinstrom/32/433_2.png) [@martinstrom](https://forum.mautic.org/u/martinstrom)\ **Post date:** [August 21, 2020, 7:43am UTC](https://forum.mautic.org/t/upgrade-error-from-2-16-3-to-3/15714/3 "2020-08-21T07:43:41Z")
I solved it! The instance didn’t load, and it did not help to clear cache folder. I could not even run any cli commands. So I ended up just removing the whole Mautic root folder (after taking a backup on the config file & media folder) and reinstalled the 2.16.3 from github and then run the upgrade, then it worked. 😀 ---
**Author:** ![silavapi](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.mautic.org/silavapi/32/7424_2.png) [@silavapi](https://forum.mautic.org/u/silavapi)\ **Post date:** [August 21, 2020, 9:14am UTC](https://forum.mautic.org/t/upgrade-error-from-2-16-3-to-3/15714/4 "2020-08-21T09:14:09Z")
How did you originally install Mautic, out of interest? ---
**Author:** ![martinstrom](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.mautic.org/martinstrom/32/433_2.png) [@martinstrom](https://forum.mautic.org/u/martinstrom)\ **Post date:** [August 26, 2020, 3:40pm UTC](https://forum.mautic.org/t/upgrade-error-from-2-16-3-to-3/15714/5 "2020-08-26T15:40:17Z")
I have installed it by just downloading the release zip a year ago. But I know we have added the composer later on and some plugins to the installation so it can have been something of this that made some conflict with it.?