Can you issue a SELECT @@version; query on the MySQL instance and report the result back?

I would not expect it but perhaps they messed with the version string and the current detection cannot cope with that.

see also #12002

Check this MSDN issue, maybe it's because of Azure reporting a 5.5 server_version in handshake (not sure, never use Azure before).

Hello. I'm in the same trouble now. (I also posted this info at #12002 )
Using like most here a Azure SQL Database.

MySQL [* * *]> select @@Version;
+-----------+
| @@Version |
+-----------+
| 5.7.18 |
+-----------+

but on system summary on the settings page you see

Piwik-Version: 3.2.0
MySQL-Version: 5.6.26.0
PHP-Version: 7.0.22-0ubuntu0.16.04.1

which is the same database version, which is shown when running the status command after connecting to the database:

MySQL [* * * ]> status
+-------------
mysql Ver 15.1 Distrib 10.0.31-MariaDB, for debian-linux-gnu (x86_64) using readline 5.2

Connection id: 65385
Current database: * * *
Current user: * * @ * *
SSL: Cipher in use is AES256-SHA
Current pager: stdout
Using outfile: ''
Using delimiter: ;
Server: MySQL
Server version: 5.6.26.0 MySQL Community Server (GPL)
Protocol version: 10
Connection: * * *.mysql.database.azure.com via TCP/IP
Server characterset: latin1
Db characterset: latin1
Client characterset: utf8mb4
Conn. characterset: utf8mb4
+-------------

-- I changed (for a quick and very dirty check) line 272 in Marketplace/Api/Client.php to this (don't do that - it was just to verify if this is the problem!)

$params['mysql'] = "5.7.18"; // $this->environment->getMySQLVersion();

After that change, I could access the Marketplace.

Closing this one as there hadn't been any further reports in the last years. If anyone experiences a similar problem, feel free to create a new issue.