PDF invoices generated by custom templates are not properly displayed by gmail pdf preview

PDF invoices generated by custom templates are not properly displayed by gmail pdf preview

I tried creating several custom templates based on the classic template, and, even with minor modifications,
the pdf generated and sent to a gmail cannot be properly opened in the gmail pdf preview.

In the example attached, the content of the table that should display items, prices quantities and amount looks completely empty. Only the totals are there. Opening the pdf in acrobat however, shows everything.

steps to replicate:

1) send the pdf attached to a gmail address
2) try to use the pdf preview within gmail

Am I doing something wrong when creating custom templates?
Or something in the pdf generation process zoho uses is not compatible with gmail preview?

Regards