@Pavan Can you please ensure that your web app is on the basic tier or higher? The free/shared tier does not support PDFs from what I last heard.
Microsoft SQL Reporting Framework manually generating PDFs
This usage pattern does not work for Free/Shared plans due to the sandbox. However, a small set of APIs are opened for use in Basic+ plans; these APIs are designed to enable SQL Reporting framework creation of PDFs. So these libraries should be usable for PDF generation in Basic+.
PDF generation from HTML
There are multiple libraries used to convert HTML to PDF. Many Windows/.NET specific versions leverage IE APIs and therefore leverage User32/GDI32 extensively. These APIs are largely blocked in the sandbox (regardless of plan) and therefore these frameworks do not work in the sandbox.
There are some frameworks that do not leverage User32/GDI32 extensively (wkhtmltopdf, for example) and we are working on enabling these in Basic+ the same way we enabled SQL Reporting.
@brtrach-MSFT Currently Application in s2 service level. we tried in s2,s3 and PC3 level Reports are rendering fast but not able to download in all service level for 1 month data. able to download only 15 days data.
@Pavan , this sounds to be an issue with the SQL reporting and not from the web app since some of the reports are working. I would suggest posting this to a SQL forum to see what they have to say on the matter as I have reviewed our internal resources and the only times I can find issues with SQL reporting it either worked 100% or it didn't work at all. We request you troubleshoot the SQL reports.
If your research shows the SQL reports to not be at fault, we can enable you for a free web apps support ticket. Please note they will only be able to assist if it is indeed the platform causing the issue.