I believe for every page that you want to include in your sitemap, you have to go to the tab Search engine → vertical tab Sitemap and then check the checkbox “Include this page in the sitemap?”.
This should output the SQL query (that is used for the sitemap) to the error log (when you run the snippet).
Then check the WHERE clause of the SQL query to make sure your resources meet all the conditions. Or maybe run the query in phpMyAdmin to test it.
Sitemap SQL-Query=SELECT modResource.*, SeoSuiteResource.id AS SeoSuiteResource.id, SeoSuiteResource.keywords AS SeoSuiteResource.keywords, SeoSuiteResource.resource_id AS SeoSuiteResource.resource_id, SeoSuiteResource.use_default_meta AS SeoSuiteResource.use_default_meta, SeoSuiteResource.meta_title AS SeoSuiteResource.meta_title, SeoSuiteResource.meta_description AS SeoSuiteResource.meta_description, SeoSuiteResource.index_type AS SeoSuiteResource.index_type, SeoSuiteResource.follow_type AS SeoSuiteResource.follow_type, SeoSuiteResource.sitemap AS SeoSuiteResource.sitemap, SeoSuiteResource.sitemap_prio AS SeoSuiteResource.sitemap_prio, SeoSuiteResource.sitemap_changefreq AS SeoSuiteResource.sitemap_changefreq, SeoSuiteResource.canonical AS SeoSuiteResource.canonical, SeoSuiteResource.canonical_uri AS SeoSuiteResource.canonical_uri, SeoSuiteResource.editedon AS SeoSuiteResource.editedon FROM modx_site_content AS modResource JOIN modx_seosuite_resourceSeoSuiteResource ON SeoSuiteResource.resource_id = modResource.id WHERE ( ( modResource.context_key IN (‘web’) AND modResource.published = 1 AND modResource.deleted = 0 ) AND ( SeoSuiteResource.index_type = ‘1’ AND SeoSuiteResource.follow_type = ‘1’ ) AND SeoSuiteResource.sitemap = ‘1’ AND modResource.class_key != ‘modSymLink’ )
If you run this query in phpMyAdmin, do you get any results?
SELECT modResource.*, SeoSuiteResource.*
FROM modx_site_content AS modResource
JOIN modx_seosuite_resource SeoSuiteResource ON SeoSuiteResource.resource_id = modResource.id
WHERE modResource.context_key IN ('web')
AND modResource.published = 1
AND modResource.deleted = 0
AND SeoSuiteResource.index_type = '1'
AND SeoSuiteResource.follow_type = '1'
AND SeoSuiteResource.sitemap = '1'
AND modResource.class_key != 'modSymLink'
If not, does this query return anything?
SELECT modResource.*, SeoSuiteResource.*
FROM modx_site_content AS modResource
JOIN modx_seosuite_resource SeoSuiteResource ON SeoSuiteResource.resource_id = modResource.id
If yes, add the WHERE conditions one by one to see where it breaks.