First, are you sure your 555 is actually operating at 38Khz? The 1838 has a bandpass filter so you need the 555 to be close to 38k.
Second, according to the 1838 data sheet, it will not respond to a continuous stream.
From data sheet
The distinguishing mark between data signal ( not
suppressed) and disturbance signal (supressed) are
carrier frequency, burst length and Signal Gap Time
(see diagram below).
The data signal should fullfill the following condition:
• Carrier frequency should be close to center frequency
of the bandpass (e.g. 38kHz).
• Burst length should be 6 cycles/burst or longer.
• After each burst a gap time of at least 9 cycles is
neccessary.
• The data format
should not make a continuous
signal transmission. There must be a Signal Gap Time
(longer than 15ms) at least each 90ms
https://www.electro-tech-online.com/custompdfs/2010/10/tsop1836.pdf