Invalid Amount Response from PayFlowPro

[JocularGargoyle]

I'm sending an HTTP request for Payflow Pro to the sandbox at https://pilot-payflowpro.paypal.com. The string I'm sending (with redactions) is below. The amount has two decimal places, as it should, but I'm still receiving an invalid amount response. Oddly, if I send it without the decimal  -- just 48 -- it authorizes. I also tried using 48.16 just in case it didn't like having 0 cents, but that also got an Invalid Amount response. Everything I've read (and Googled up when researching this) says the amount should include a decimal to two places, so what might be going wrong here? I found one issue where it could throw an error if the address had a period in it (like Rd. Or Ave.) but I don't even have that parameter. Thanks!

USER=xxx&VENDOR=xxx&PARTNER=paypal&PWD=xxx&TRXTYPE=S&TENDER=C&ACCT=4111111111111111&EXPDATE=0323&CVV2=123&ZIP=32301&AMT=48.00

[AlexSafian]

Just a guess -- try telling it how long the amount string is, like this &AMT[5]=48.00

[Payflow_Todd]

Something else is wrong or we are receiving the data incorrectly.  Does the amount show up correctly in Manager?  Reach out to Payflow support and they can look up the PNREF of failed transaction and check that we are receiving the data correctly.

Todd