Tankless require yearly service to keep burner and combustion parts clean and check electrical connections, gas solenoid, gas pressure, venting, etc.
Read product manual for advisories and recommended maintenance.
Yes, aren't you glad you saved the manual.
Always check that local area has affordable and qualified service technician for your brand before buying tankless.
Before calling service technician, copy following link for general troubleshoot resources, including some manuals, and links to Bosch.http://waterheatertimer.org/pdf/No-Error-Code.pdfhttp://waterheatertimer.org/Troubleshoot-Bosch-Tankless-water-heater.html
Try turning temperature down.
The fact there is no error code, and the gas is not firing correctly, means you have a small unit with no error codes and PC board has failed ... or it means you have a unit with error codes and possibly bad PC board.
If problem is the PC board, then Bosch will send you new board, and expect same level of repair success as though your computer's motherboard was replaced.
You can buy ordinary box-store tank-type heater and install yourself same day for about $325.
Then maintain and fix it yourself. I recommend AO Smith/American/State/Reliance/Kenmore/Whirlpool since these are easy to maintain with clear directions in manual, plus AO Smith posts service manuals for the whole line of products, and any local plumber can fix them with ez-to-locate generic parts.http://waterheatertimer.org/How-to-install-gas-water-heater.html