If you can log into your host with SSH or FTP, it’s an easy fix. Like the comments said before, check your permissions for the WordPress directory. For example, if you check the hosting directory with ls -al (typically /var/www, as on DigitalOcean), they should look something like this:
drwxrwxr-x 6 www-data www-data 4096 Nov 14 17:00 wordpress
That means both the user and group has write permissions set. To make sure those are set correctly, you can use this command on the directory:
sudo chmod ug+w wordpress
Also, make sure the user and group ownership is set correctly. In the above example, the server daemon is run under the www-data user and group (it could also be httpd). To set the directory’s ownership to www-data you can run the command chown like this:
sudo chown -R www-data:www-data wordpress
If you’re using an FTP client, try right-clicking the wordpress directory and using its Permissions functionality to set the permissions and ownership (will vary from FTP app to FTP app).
Hope this helps!