WinRed, the payment processor for Republican campaign donations, crashed after former President Donald J. Trump’s felony conviction, a technical issue that his campaign attributed to the number of people trying to donate in the immediate aftermath of the verdict.

“So many Americans were moved to donate to President Trump’s campaign that the WinRed pages went down,” the Trump campaign said in a statement on social media.

The website no longer shows an error message when visiting the donation page for Trump’s campaign, though it is unclear if the website is properly functioning and processing donations. The Trump campaign did not immediately respond to a request for comment.

Mr. Trump began soliciting donations off his felony conviction almost immediately after the verdict was read from the Manhattan courthouse. In statements on his social media website, Truth Social, Mr. Trump posted links to the campaign’s website; it redirected to the WinRed page, which was not working properly.

That donation page features a large image of Mr. Trump’s mug shot, which was taken in Atlanta after Mr. Trump surrendered at the Fulton County jail in his Georgia criminal case, with the caption “Never surrender.” The page also describes Mr. Trump as a “political prisoner” and called on “TEN MILLION pro-Trump patriots” to donate by the end of the day.