Can’t run WP installer

And your website url is?

My website url is https://blog.dansmithvisuals.com

Your main domain is running WP as well. Could you check if you’ve properly configured your subdomain? I mean if it points to the folder where you have your blog installed. Did you make complete FTP transfer of the WP installation? Maybe something went missing in the process somehow.
Also is there a chance that you try to use Softaculous installer on your subdomain?
And finally, what’s inside your main .htaccess file?

I am not sure if the subdomain was created correctly, because my client created it for me. Unfortunately I do not have access to hosting panel.
I think that all files were transferred successful, I even tried to re-upload WP.
It is main .htaccess file

# BEGIN WordPress
AddHandler application/x-httpd-php70s .php
<IfModule mod_expires.c>
	ExpiresActive On
	ExpiresByType image/jpg "access plus 1 year"
	ExpiresByType image/jpeg "access plus 1 year"
	ExpiresByType image/gif "access plus 1 year"
	ExpiresByType image/png "access plus 1 year"
	ExpiresByType text/css "access plus 1 month"
	ExpiresByType application/pdf "access plus 1 month"
	ExpiresByType text/javascript "access plus 1 month"
	ExpiresByType image/x-icon "access plus 1 year"
	ExpiresDefault "access plus 1 weeks"
</IfModule>
Options -Indexes
<IfModule mod_rewrite.c>
	RewriteEngine On
	RewriteBase /
	RewriteRule ^/wp-content/endurance-page-cache/ - [L]
	RewriteCond %{REQUEST_METHOD} !POST
	RewriteCond %{QUERY_STRING} !.*=.*
	RewriteCond %{HTTP_COOKIE} !(wordpress_test_cookie|comment_author|wp\-postpass|wordpress_logged_in|wptouch_switch_toggle|wp_woocommerce_session_) [NC]
	RewriteCond %{DOCUMENT_ROOT}/wp-content/endurance-page-cache/$1/_index.html -f
	RewriteRule ^(.*)$ /wp-content/endurance-page-cache/$1/_index.html [L]
</IfModule>
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>

# END WordPress  

I tried to disable it, but also without any success.

If you’ve also disabled (renamed) .htaccess and it didn’t make any change then I’m out of fresh ideas. ??

Neverthelessб thank you for trying to help!

You’re welcome. The only remaining item would be for you to get to cPanel and double-check the subdomain setup and try Softaculous installation.

Ok, thanks!