Seem to have messed up Admin backend

Magento 2
2

Hi @damianduffy,

As of yet, I’ve not come across this issue before. Did you:

  1. Run composer require mageplaza/module-smtp as the magento file user (not root)?
  2. Run composer require mageplaza/module-smtp from within the Magento root directory?

Developer Mode
If you’re working in Developer Mode, try running the following series of commands (from Magento root directory as magento file user):

  1. rm -rf var/cache var/log var/page_cache var/view_preprocessed
  2. bin/magento setup:upgrade

Production Mode
If you’re working in Production Mode, try running the following series of commands (from Magento root directory as magento file user):

  1. bin/magento setup:di:compile
  2. bin/magento setup:static-content:deploy en_GB en_US
  3. bin/magento cache:flush

Note: In step 2, I deploy static content in the the languages that I’ve been working in. So, I always add en_US and my stores use en_GB locale. So, I add both.

Permissions and Ownerships
Also, check that your Folder/File permissions are correct by running ls -la within the Magento root directory. In many cases, I’ve found a common cause of issues are down to either a) File/Folder Ownership or b) File/Folder Permissions.

Side-note
Mageplaza SMTP randomly stopped working for me a few months ago (not related to this issue). As an alternative, if you’d like another option try Ebizmarts SMTP. It’s worked fine for me, and the devs still support it.

Please, let us know how you get on.

Disclaimer: Always backup your files/database/server before executing any commands when debugging - As blindly executing commands may make things worse.