Error: "No device found on target" when attempting to program custom STM32F401 PCB w/ STLINK V2

[Ant1pattern]

I've designed a custom PCB incorporating STM32F401RE. I've received the first batch of PCB and attempted to program one, but STM32CubeIDE raises the error line as in the title ("No device found on target").

I've kept the design (see image) as close as possible to the Nucleo64-F401RE, and also cross-checked AN4488 ("Getting started with STM32F4xxxx MCU hardware development").

I couldn't find any red flags so far, but maybe some of the fellow forum members could give me a critique of the design. Am I missing crucial details?

Please note that I've deleted a good number components that are not required for programming; These are not yet soldered onto the PCB so the schematic reflects the circuit as-is.

I further run tested a number of basic tests which mostly came out ok:

• Supply voltages (5V, 3.3V) are stable and dont appear to have noticable consumption
• No warming of anything on the PCB
• No short circuits in the between the pins of the IC
• All pins seem to have contact
• Scope shows sensible signals (3.3V, RESET, SWCLK, SWDIO) on the appropiate pins. I've not went into the details here, nothing seen on SWO though.
• 3.3V and GND can be seen on the appropiate pin of the STLINK
• Checked the orientation of the IC and it appears to be correct (the enclosure featured not one but two dots; so I cross-checked with my Nucleo64, and after this I believe the smaller dot indicates pin 1)
• VCAP1 reads a mere 0.3V instead of 1.25V (source here)

I hand-soldered the board and it is thus possible that I've damaged the IC doing so. However I am experienced in the matter and considering the current supply situation I made very sure that I am handling the device well.

I have a second, spare IC to check against - but right now I'd like to avoid that, because it will be nearly impossible to get a replacement at the moment.

Thanks for your attention and I would be very glad about some pointers.

Best regards

Addendum: Here's the log from STM32CubeIDE:

STMicroelectronics ST-LINK GDB server. Version 5.8.0
Copyright (c) 2020, STMicroelectronics. All rights reserved.
 
Starting server with the following options:
        Persistent Mode            : Disabled
        LogFile Name               : C:\***\st-link_gdbserver_log.txt
        Logging Level              : 31
        Listen Port Number         : 61234
        Status Refresh Delay       : 15s
        Verbose Mode               : Enabled
        SWD Debug                  : Enabled
        InitWhile                  : Enabled
 
Target connection mode: Under reset
Target connection failed
Target no device found
 
Error in initializing ST-LINK device.
Reason: No device found on target.

[TDK · Accepted solution]

Pin 13 is VDDA/VREF+ (not just VREF+). You'll need to connect this to VDD. This means you won't be able to have a voltage reference source separate from VDD.

[Ant1pattern]

Right! Of course, that was also mentioned in the thread I linked. My KiCAD symbol hat the pin labeled as VRef+ and I was lazy checking. That seemed to do the trick.

Thank you very much.