Alurb52gmailcom I have the same problem. Since 04Jan24 ToDo app crashes on my MacBook Pro (early 2013; ver 10.15.7). No change in the Mac OSX.

Found similar problem for Mac in Msoft community site (June 2023 user SLS212)

Microsoft TO DO keeps crashing when opened

https://answers.microsoft.com/en-us/msoffice/forum/all/microsoft-to-do-keeps-crashing-when-opened/e2a4bba5-5d01-4b33-bf00-138d620ba87b?correlationid=4c3d3a4f-3760-4927-8c69-e66bcf24fc99&from=ContactUsWebBCQR

I tried all the suggestions listed (each time deleting the todo app and restarting incl. shutdown):

1. deleted cache 

2. deleted group container

3. deleted todo.mac container

Same result: Each time crashes. Still crashing today.

Today got hold of msoft agent (waited all day yesterday no response). Agent says To Do has NO EXPERT SUPPORT so Msoft releases and app without any link to the developers. Nice one!

The only thing I see has changed (for me) is the new feature 'category sort' released this week. Sort for open tasks (say in My Day) includes categories now. 

As To Do is able to link to Outlook (and Planner), this features shares categories which are set in Outlook with the To Do and Planner apps.  Unfortunately my Mac 10.15.7 DOES NOT allow ToDo to connect to my Outlook (or Planner) so integrations between apps not supported. I cannot use Planner at all, and my Outlook does not link its Tasks to the To Do app (although it is designed to do so).

I suspect this may be my issue.  

I saw somewhere else that someone had identified conflicts with Outlook and To Do categories. They deleted the tasks assigned to categories in Outlook where the associated category had been deleted (I suspect that user may have later version of Mac which DOES connect to Outlook).

Meanwhile all I can do is login to the web version on my Mac and workaround the issue until Msoft decides to solve the issue. I expect this may never happen for 10.15 users as this is the oldest version included with the app setup.

Good Luck!

======

My crash report (I have had 10x and each time its the same exception/termination codes)

Process: Microsoft To Do [2494]
Path: /Applications/Microsoft To Do.app/Contents/MacOS/Microsoft To Do
Identifier: com.microsoft.to-do-mac
Version: 2.112 (231214.1820)
App Item ID: 1274495053
App External ID: 862498887
Code Type: X86-64 (Native)
Parent Process: ??? [1]
Responsible: Microsoft To Do [2494]
User ID: 501

Date/Time: 2024-01-05 11:46:30.802 +0000
OS Version: Mac OS X 10.15.7 (19H2026)
Report Version: 12
Anonymous UUID: 0AA2B060-46EE-E907-F5B3-ADA42A5D6C17

Time Awake Since Boot: 10000 seconds

System Integrity Protection: enabled

Crashed Thread: 0 Dispatch queue: com.microsoft.oneAuthContextQueue

Exception Type: EXC_BAD_ACCESS (SIGSEGV)
Exception Codes: EXC_I386_GPFLT
Exception Note: EXC_CORPSE_NOTIFY

Termination Signal: Segmentation fault: 11
Termination Reason: Namespace SIGNAL, Code 0xb
Terminating Process: exc handler [2494]