Mailed my 2019 Federal tax return on April 16th, I still didnt receive any refund plus I cannot track my refund through IRS.gov, any suggestions about that?

Sorry the IRS has limited staff due to Covid-19.  They just started opening the mail in June that's been stacking up. Back in March the IRS closed their processing centers and stopped processing mailed tax returns.  An IRS spokesperson recently said that they have about 11 million pieces of unopened mail.  The IRS says....."We’re experiencing delays in processing paper tax returns due to limited staffing. If you already filed a paper return, we will process it in the order we received it."  So it may take longer if you mailed in June or later.  So you have to keep waiting.

See this IRS page for the latest information

https://www.irs.gov/newsroom/irs-operations-during-covid-19-mission-critical-functions-continue