Can't install extension from marketplace and with composer

[akhundof]

Dears, i had created new magento storage (version 2.2.6). Right now i had installed theme and one extension with composer. I had connected My Web Extension manager to my magento market account, but it not shows any installations regarding my modules. Nevertheless i had installed one module with composer by guide (INSTALLATION LINK) . But now i had a problem installing module module link . Composer gives me error 

  [InvalidArgumentException]                                                                                                                                                      
  Could not find a matching version of package ulmod/ordercomment. Check the package spelling, your version constraint and that the package is available in a stability which ma  
  tches your minimum-stability (stable).

What can be a reason, does it means that i can't install this module to this version of magento ? File installation to coping it to app/code/ seams to be fine , but Store->Configuration stopped working complitely. Please help me to find solution. Thanks in advance. 

[md. ehsanul haque _kanan]

I think the module is not compatible with the current version of your Magento website. Contact the developer of the module for further clarification.

[akhundof]

I had installed module manually by downloading it from original site, but not from market place ( 

[akhundof]

Can anyone explain me, why my Extension Manager can't load any extension and work in very very slow way. I can't see installed extension from market. 

[md. ehsanul haque _kanan]

Try downloading from the marketplace. It should work.

[hukuhn]

Might be the same issue I'm having: https://community.magento.com/t5/Installing-Extensions/Magento-Repo-packages-json-slow-to-update/m-p...

Maybe a system issue at Magento today?

[emily_nguyen]

Hi,

I found this instruction helpful and think you may want to take a look: https://beeketing.com/blog/install-magento-extensions/

I've followed their guide and successfully installed this plugin https://marketplace.magento.com/beeketing-magento-beeketing.html 

Let's try again. Let me know if you need my help.

[daksha_ps]

Install Magento 2 extension in 3 Simple methods

Magento extensions can be installed in 3 different ways: via Composer, via ZIP-archive, and via Browser. The choice of method depends on the way the module appears in the system.

Method 1, Installing the extension from third-party resources.

Method 2, Install the extension from Magento Store.

Method 3, Install via admin web setup wizard.

Now, let's dive into the methods to Install Magento 2 Extension..